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Abstract:

A wave energy converter includes a buoy and a transmission unit. In the
transmission unit there is a driveshaft, which is driven to rotate either
when the buoy rises or sinks, yet always in the same direction. The
driveshaft is mechanically coupled to one of the rotating parts of an
electric generator and drives this to generate electric current. Further
on there is an energy accumulation device, which is also coupled to the
driveshaft to accumulate energy when the buoy rises or sinks and the
driveshaft rotates and which is then used to drive the generator at the
other of the rising and sinking motions. The coupling between the energy
accumulation device and the driveshaft can go by the generator's second
rotatable part, the air gap between the generator's parts and the
generator's first part. The coupling over the air gap gives a torque,
which drives the second part to rotate along and which also counteracts
the rotation of the driveshaft. The generator's second part is driven by
the energy accumulation device to rotate in the other direction, when the
torque from the driveshaft does not exceed the counteracting torque.

Claims:

1. A wave energy plant comprising:a buoy or other device arranged at or in
a pool of water to be put into motion by motions of the water in the pool
of water,a driveshaft, which is rotatably journalled in bearings to the
buoy resp. the other device or to a device arranged to give a
counteracting force against the motions of the water in the pool of
water,a first oblong organ, which in one end is coupled to a device
arranged to give a counteracting force against the motions of the water
in the pool of water resp. to the buoy and in the other end is coupled to
the driveshaft,an electric generator, which is coupled to the driveshaft
and includes two in relation to each other rotatable parts, a first part
and a second part, andan energy accumulation device, at which the buoy or
the other device is placed and the buoy or the other device, the first
oblong organ, the device arranged to give a counterforce against the wave
motions, the driveshaft and the energy accumulation device are coupled
together, so that the coupling between the first oblong organ and the
driveshaft gets the driveshaft to mainly at the first motions in the buoy
or the other device, rotate in a unidirectional direction and thereby
drive the electric generator's two mentioned parts to rotate in relation
to each other in a first rotational direction and generate electric
current and thereby also supply the energy accumulation device with
energy, characterized in that wherein the energy accumulation device is
arranged to mainly at the second motions, which are mainly separated from
the first motions, in the buoy or the other device, drive the electric
generator's mentioned two parts to rotate in the same first rotational
direction in relation to each other and thereby to generate electric
current with the same polarity as when the driveshaft drives the electric
generator's two mentioned parts to rotate in relation to each other.

2. A wave energy plant according to claim 1, comprising a buoy, which is
arranged to alternately rise and sink and/or to alternately rock back and
forth at the up and down motions of the water surface, and the buoy, at
which the first motions in the water surface includes either one of the
up- and down-going motions of the water surface.

3. A wave energy plant according to claim 1, whereinthe driveshaft is
mechanically coupled with the generator's first part, at which an
electromagnetic coupling exists over an air gap between the electric
generator's first and second parts at least during these parts relative
movements, andthe energy accumulation device is mechanically coupled to
the second part of the electric generator.

4. A wave energy plant according to claim 3, wherein the coupling of the
energy accumulation device to the driveshaft via the electric generator's
second part and the electric generator's first part and the air gap
between them gives a counteracting motive force, which counteracts the
rotation of the driveshaft, when the driveshaft through the coupling
between the first oblong organ and the driveshaft rotates and drives the
electric generator's first part,so that the electric generator's second
part rotates in a first rotational direction through the coupling to the
driveshaft via the electromagnetic coupling over the air gap and the
electric generator's first part, when the motive force which acts on the
driveshaft through the coupling between the first oblong organ and the
driveshaft, exceeds the counteracting motive force at which the energy
accumulation device through its mechanical coupling to the electric
generator's second part accumulates energy, at which the electric
generator's first and second parts at the same time rotates in the same
first rotational direction in relation to each other, andso that the
electric generator's second part is driven by the energy accumulation
device to rotate mainly in the same first rotational direction, when the
motive force, which acts on the driveshaft through the coupling between
the first oblong organ and the driveshaft, do not exceed the
counteracting motive force, at which the electric generator's first- and
second parts is made to continue to rotate in the same first rotational
direction in relation to each other.

5. A wave energy plant according to claim 1, comprising:a mechanical gear
coupled between the driveshaft and the electric generator's first part,
at which the driveshaft is coupled to the ingoing side of the mechanical
gear and the electric generator's first part is coupled to a first
outgoing side of the mechanical gear, at whichan electromagnetic coupling
exists over an air gap between the electric generator's first part and
second part at least during their relative movements,the electric
generators second part is fixed to the buoy, andthe energy accumulation
device is mechanically coupled to a second, from the first separated,
outgoing side of the mechanical gear.

6. A wave energy plant according to claim 5, wherein the mechanical gear's
ingoing side includes an ingoing shaft and one outgoing side of the
mechanical gear includes an outgoing shaft and one other outgoing side
includes a housing or casing for the mechanical gear.

7. A wave energy plant according to claim 1, comprising an anchor drum,
which is journalled in bearings for rotation in a unidirectional rotation
around the driveshaft and is coupled to the first oblong organ to bring
the anchor drum to rotate with the mentioned first motion of the buoy or
the other device and thereby also bring the driveshaft to rotate.

8. A wave energy plant according to claim 7, wherein the first oblong
organ is a flexible organ, a line, wire or chain in particular, which in
one end is more or less winded up on an anchor drum, and that a mechanism
exists for at the mentioned second of the buoy's or the other device's
motions, rotate the anchor drum so that the flexible organ is kept in a
stretched state.

9. A wave energy plant according to claim 7, wherein the bearing for a
unidirectional rotation of the anchor drum around the driveshaft, which
enables the anchor drum during rotation in the opposite direction to
drive the driveshaft to rotate in the opposite direction, includes a
coupling for limitation or disengagement of the motive force, with which
the anchor drum hereby acts on the driveshaft.

10. A wave energy plant according to claim 1, wherein the driveshaft is
journalled in bearings at a buoy and that the first oblong organ in one
end is coupled to a point which counteracts to the buoy's motions,
especially to a fixed point like at the bottom of the pool of water or to
a fixed of fastened device at the bottom of the pool of water.

11. A wave energy plant according to claim 1, wherein the driveshaft is
rotatably journalled in bearings to one at the pool of water fixed device
and that the first oblong organ in one end is coupled to a buoy.

12. A wave energy plant according to claim 11, wherein the driveshaft is
placed below the water surface and that the energy accumulation device
includes at least one floating body.

13. A wave energy plant according to claim 1, wherein the driveshaft is
rotatably journalled in bearings to the buoy and that the first oblong
organ in one end is coupled with a weight, which is resiliently suspended
to the buoy.

14. A wave energy plant according to claim 1, wherein the buoy includes a
space, which functions as an air pocket and in which at least the main
part of the driveshaft is located.

15. A wave energy plant according to claim 1, wherein the energy
accumulation device includes a counterweight arranged as a lead which
moves upwards at the mentioned first of the buoy's or the other device's
motions and at which potential energy is stored, that the coupling
between the buoy or the other device, the first oblong organ, the
driveshaft and the counterweight is arranged in a way, that the
counterweight moves downwards at the mentioned second motion of the buoy
or the other device and that the counterweight drives the generator's
first and second parts to rotate in relation to each other in the first
rotational direction.

16. A wave energy plant according to claim 15, wherein the energy
accumulation device includes a counterweight drum rotatably journalled in
bearings to the driveshaft and a second oblong organ for coupling of
motions in the counterweight to drive the counterweight drum to rotate,
at which the driveshaft is coupled to rotate the electric generator's
first part and the counterweight drum is coupled to rotate the electric
generator's second part, at which the electric generator generates
electric current when its second part rotates in relation to its first
part at the same time as it gives a counteracting torque to this
rotation, at which the electric generator's first and second parts is
brought to rotate in relation to each other, always in the same first
rotational direction.

17. A wave energy plant according to claim 15, wherein the energy
accumulation device includes a counterweight drum rotatably journalled in
bearings to the driveshaft and a second oblong organ for coupling of
motions in the counterweight to drive the counterweight drum to rotate
and that a mechanical gear is coupled between the driveshaft and the
electric generator's first part, at which the driveshaft is coupled to an
ingoing side of the mechanical gear, the electric generators first part
is coupled to an first outgoing side of the mechanical gear, the electric
generator's second part is fixed to the buoy or the other device and the
counterweight drum is mechanically coupled to a second, from the first
separated, outgoing side of the mechanical gear, so that the driveshaft
at the mentioned first motions in the buoy or the other devices gives
motive forces on both outgoing sides of the mechanical gear for rotation
of the electric generator's first part and for rotation of the
counterweight drum to hoist up the counterweight in relation to the
driveshaft and so that the counterweight drum at the mentioned second
motions in the buoy or the other device gives a motive force via its
coupling to the gear's second outgoing side for rotation of the electric
generator's first part.

18. A wave energy plant according to claim 1, wherein the energy
accumulating device includes a counterweight drum and a counterweight and
that the second oblong organ is a flexible organ, a line, wire or chain
in particular, which in the lower end is fixed to the counterweight and
its upper end is more or less winded up on the counterweight drum.

19. A wave energy plant according to claim 1, comprising a control system
for controlling the electric generators electric load or field current
for adjusting the rotation speed between the electric generator's first
and second parts.

20. A wave energy plant according to claim 19, wherein the energy
accumulation device includes a counterweight or a floating body and that
the control of the electric generator's electric load or field current
also is used for adjusting the counterweight's resp. floating body's
vertical speed, so that the counterweight resp. the floating body moves
within an adapted or suitable vertical span at the motions of the buoy or
the other device.

21. A wave energy plant according to claim 20, wherein the control system
is arranged to compensate for variations in the torque, which is caused
by the levy in mass of the counterweight resp. floating body, by
regulation of the rotation speed between the electric generator's first
and second parts, which gives a continuous even power output from the
electric generator.

22. A wave power plant according to claim 1, wherein it includes two
electric generators and two belonging energy accumulation devices coupled
to the driveshaft, at which the first oblong organ is coupled to the
driveshaft to a place located between the two pairs of electric generator
and belonging energy accumulation device.

23. A wave power plant according to claim 1, wherein the first oblong
organ at least in one end includes two sub organs, at which a first sub
organ is coupled to the driveshaft on one side of the electric generator
and another sub organ is coupled to the driveshaft on the opposite side
of the electric generator.

24. A wave energy plant according to claim 1, wherein it includes an
anchor drum coupled to the first oblong organ and that the first oblong
organ includes a flexible organ, a line, wire or chain in particular,
which at least in one of its ends is divided into two sub organs, which
each one is more or less winded up on the corresponding wind up surfaces
of each anchor drum, at which the wind up surfaces have helicoidally
running grooves with opposite helicoidal directions.

25. A wave energy plant according to claim 1, wherein the energy
accumulation device includes two counterweight drums journalled in
bearings to the driveshaft and a flexible organ, a line, wire or chain in
particular, which at least in one of its ends is divided in two flexible
sub organs, which each one is more or less winded up around corresponding
wind up surfaces on the counterweight drums, at which the wind up
surfaces has helicoidally running grooves with opposite helicoidal
directions.

26. A method of extracting electrical energy from more or less periodical
motions of a body, especially repeated back and forth motions and/or
repeated rocking motions in two opposite directions, whereinthat at the
first motions of the body let these motions drive two parts of an
electric generator to rotate in relation to each other in a first
direction and hereby generate electric current and at the same time also
supply an energy accumulation device with mechanical energy, andthat at
the second motions of the body, which mainly is separated from the first
motions, let the energy accumulation device drive the electric generators
two parts to rotate in the same first direction in relation to each other
and thereby generator electric current with the same polarity as at the
first motions of the body.

[0002]The present invention relates to a wave power plant for extraction
of electrical energy from motions of water waves, a method of extracting
electrical energy from more or less intermittent mechanical energy, such
as more or less periodical motions in a body, and a transmission for
power plants to be used when such more or less intermittent mechanical
energy is available.

BACKGROUND

[0003]Wave power has a large potential of becoming cost efficient since
the energy density in ocean waves is very high (approximately 1000 times
higher than in the wind), this allowing small wave energy converters in
relation to the capacity thereof. Furthermore, wave energy is more
predictable than for instance wind power since waves are built by the
wind during a long period of time and then continues as swell also after
the wind has subsided. This results in slow variations in the average
energy content of the waves, which gives system advantages when wave
energy converters are connected to the general electric power
distribution network.

[0004]A reason why, in spite of this potential, there are so few
competitive solutions today is that wave energy is difficult to master.
The ocean is a rough environment with high material stress. In stormy
weather the energy levels can be a 100 times higher than normal. The wave
motion is oscillating and with never ceasing variations in height, length
and time period (velocity) from wave to wave, this giving large
variations in the energy absorbed by a wave power plant. For direct
driven operation, i.e. when the generator in the wave power plant is
driven according to the momentary motion of the wave, this results in a
low utilization of the power plant, i.e. the so called capacity factor
takes a low value. The power of the generator shifts between zero and a
top level twice every wave period. The top level may also change very
strongly from wave to wave. The general electric power distribution
network requires relatively stable levels, both in delivered power and
voltage, this resulting in that the electrical control systems for this
kind of wave energy converters must, after the generation, make the
levels of these more even. Also, the uneven levels results in a costly
over-dimensioning of the total electrical system of a wave power plant in
order to obtain a proper handling of the top power levels.

[0005]To make wave power competitive a wave power plant is required that
can efficiently absorb the wave energy at the same time as the motive
force on the generator is leveled, so that a higher capacity factor is
obtained. Also, a low system complexity and an efficient use of
components are required. The structure of the wave power plant must also
be storm proof and have a long life-cycle, and low operational and
maintenance costs that can be achieved by a construction allowing long
service intervals and includes wearing parts that can be easily accessed.

[0006]Wave power technology has been developed for a long period of time
but so far it has not been possible to arrive at a method or a design of
a wave power plant, where it has been possible to combine the necessary
properties as described above.

[0007]A frequent method of capturing the energy of water waves is to use
the vertical motion of the water. Installations that use such technology
are sometimes called "point absorbers". One way of using the vertical
motion incorporates a buoy having a bottom foundation and an anchor
wheel. The bottom foundation is firmly positioned at the sea-floor and is
connected to the buoy which follows the ocean surface, i.e. the wave
motions. When the surface rises and thereby lifts the buoy, a motive
force is created, which is converted to a rotational motion by a
driveshaft connected between the foundation and the buoy or by a wire or
chain, which runs over an anchor wheel journalled in bearings at the buoy
or in the foundation and which at an opposite end is connected to the
foundation or the buoy, respectively. The motive force increases due to
the increased motion speed of the waves when the wave height becomes
higher. The rotational direction and speed of an anchor wheel, is such a
wheel is used, is directly dependent on the vertical direction and motion
speed of the waves. However, this is not optimal for coupling a
conventional generator to the anchor wheel to produce electric energy.

[0008]In order to make a wave power plant driving a conventional rotating
generator efficient, the vertical motion of the waves must be converted
into a unidirectional rotational movement, and the rotation speed of an
electrical generator connected to the transmission must be stabilized. In
a device, as described above, using a driveshaft, wire or chain, which is
secured to the sea bottom or in a frame structure and which runs along or
over an anchor wheel journalled in a buoy, this problem can be solved in
the following way. When the buoy is lifted by a wave, a motive force over
the anchor wheel is created. Thereupon, when the wave falls, an
anti-reverse mechanism is disengaged and the anchor wheel is returned by
a counterweight. Then, the motive driving is only active during the rise
of the wave and ceases completely when the wave sinks, which is not
satisfactory. Attempts have been made to reverse the rotation direction,
so that an electrical generator driven by the anchor wheel is driven by
the counterweight in the same direction also when the wave sinks. It has
also been attempted to reverse the rotation direction of the generator.
However, changing the rotation direction of a mechanical transmission or
of the generator twice for every wave period results in heavy mechanical
wear. Even though the rotation direction can made unidirectional by the
transmission, the rotation speed follows the speed of the vertical
motion, this causing that the power output from the generator varies
according to the speed of the wave motion. This gives to a low capacity
factor and high attenuating effects since the mass of the generator all
the time alternatingly be accelerated and decelerated. In order to make
the motive force and rotation speed of a generator using a mechanical
transmission multiple buoys can cooperate, a phase shift existing between
the buoys. However, this only works optimally in the case where the buoys
are evenly distributed over a wave period, which very seldom occurs the
length and speed of the waves always vary. Also, the transmission system
becomes more complex and hence hydraulic mechanisms are frequently used
in systems of this type. However, hydraulic devices results in complex
systems having large transmission losses. A wave power plant of the type
described above is disclosed in the published French patent application
2869368, which comprises a floating platform or buoy. Lines run over
pulleys at the buoy, one end of the lines being attached to the bottom
and the other end carrying a counterweight. The rotation of the pulleys
is transferred to generators. The rotation speed and power output from
the generator vary according to the motion of the waves. A similar wave
power plant is disclosed in U.S. Pat. No. 4,242,593, which drives a wheel
or pulley in the buoy only when it is rising. A gearbox is provided for
gearing up the rotation speed of the wheel or pulley in the buoy to make
it suitable to be used for driving a generator. In U.S. Pat. No.
5,889,336 and the published Japanese patent application 11-6472 a similar
wave energy plant is disclosed including a chain which at one end is
attached to a bottom foundation end and at its other end has a
counterweight. The chain passes over a chain pulley in a buoy. The chain
pulley is connected to a generator through a directly acting
transmission, which is arranged so the generator always rotates in the
same direction. The rotation speed depends on the speed of the vertical
motion of the buoy.

[0009]A wave power installation of a somewhat different type is disclosed
in U.S. Pat. No. 4,241,579. A driveshaft is mounted to be elevated and
sunk between the water surface and the bottom. A number of buoys are by
wires connected to counterweights and the lines pass around the common
driveshaft for driving only when the respective buoy. In the published
British patent application 2062113 a wave energy converter is disclosed
including a plurality of different drive mechanisms, each one of which
comprises a buoy and a counterweight/bottom foundation/additional buoy
and which act on a common driveshaft through one-way couplings. In the
published French patent application 2339071 a buoy is used, which is
connected to one end of a chain and by the chain drives a driveshaft
placed above the water surface to rotate. The other end of the chain
carries a counterweight, which is also placed above the water surface.
The connection to the driveshaft is of a unidirectional type and the
driveshaft may be driven by several such buoys through chains.

[0010]In the published International patent application WO 2005/054668 a
wave energy plant including a buoy which is attached to an end of a line
is disclosed. The other end of the line is more or less wound up around a
drum placed on the bottom of the sea. The drum is connected to a return
spring and a generator and drives the generator in both the rising and
sinking motion of the buoy. In the wave energy plant according to the
published International patent application WO 03/058054 the buoy acts as
an winding drum for a line, the lower end of which is connected to a
bottom foundation. A return spring, a gear up mechanism and a generator
are located inside the drum. The generator is driven in both the rising
and sinking motion of the buoy.

SUMMARY

[0011]It is an object of the invention to provide an efficient wave energy
plant.

[0012]In a wave energy plant energy from water waves in a pool of water
during parts of the motions of the water waves is absorbed for driving an
electrical generator. However, part of the absorbed energy is temporarily
accumulated or stored in some suitable mechanical way for driving the
electrical generator during other parts of the motions of the water
waves. Thereby, an equalization over time of the motive force, which
drives the electrical generator, can hereby achieved. For the temporary
mechanical accumulation of energy a change of potential energy can be
used, such as variations of the potential energy of a suitable body. For
example, the change of potential energy can be based on elastic forces or
on gravitational forces. In the latter case a floating body can be used,
i.e. a body having a density lower than that of water, which is located
at a varying distance from the water surface and hereby indirectly uses
the gravitational forces. The body used for accumulation of energy can in
the same case alternatively be a counterweight, i.e. a body having a
density higher than that of water, which uses the gravitational forces in
a more direct way. The body may in these cases be connected to some
elongated means, such as a line, wire or chain, which in the case where
it is flexible can be more or less wound around a counterweight drum. The
counterweight drum can be journalled at a buoy or at a stationary rack or
frame placed on or attached the bottom of a pool of water. The
counterweight drum can in one case be mechanically connected to a
rotating part of an electrical generator and the weight or buoyancy of
the body is used for continuously driving the counterweight drum to
rotate in an opposite relative rotational direction compared to the
rotational direction of a driveshaft, which is connected to another
elongated means, also here for example a line, wire or chain.

[0013]The driveshaft is mechanically arranged for a unidirectional
rotation only, driven for example by the rising or sinking motions of a
water surface or more particularly by alternatingly rising and sinking
movements and/or alternating tilting, back and forth movements of a buoy,
i.e. a body having a density lower than that of water, which is floating
at the water surface, or alternatively by some other form of oscillatory
movement or combination of oscillatory movements in the waves or in the
water. The electrical generator is in the above mentioned cases
mechanically connected in a transmission path between the driveshaft and
the counterweight drum. The electromagnetic coupling between the parts in
the electrical generator over the air gap of the generator gives a
limited torque in relation to the rotation speed of the generator, the
mechanical torque provided by the counterweight drum and the electrical
load of the generator. When the driveshaft is rotating faster than the
rotational speed in the generator, the counterweight drum is rotated in a
first rotational direction, this causing the counterweight to be hoisted
up, thereby accumulating potential energy. When the driveshaft is
rotating slower than the rotation speed in the generator or is
still-standing still, the counterweight drum rotates in a second
rotational direction, this causing the counterweight to be lowered,
thereby releasing potential energy.

[0014]As an energy accumulation device, which uses elastic forces, an
elastic or resilient mechanism may be used, in which the energy is
accumulated as a tension in a spring or generally as elastic energy. Such
an elastic device may in a different case comprise a container for
accumulation of energy as a gas pressure. The container may then be
connected to a combined compressor or gas pump and a pneumatic motor such
as a scroll pump. This device may have one moving part directly connected
to one of the parts of the generator.

[0015]In such a wave energy plant it is possible achieve, using an energy
accumulation device, also called energy storing device, and suitable
couplings, an equalization of the kinetic energy of the water waves in an
efficient way, so that the generator can be driven to continuously
generate electricity at a relatively even level.

[0016]Generally, a wave energy plant or in its most common form a power
plant using movements, such as more or less periodic motions, of the
water of a pool of water, can comprise: [0017]A buoy or other device,
which is arranged at or in the pool of water to be made, in some way, to
move by movements of the water in the pool of water. Then, the buoy or
the other device is constructed and placed so that it itself, because of
movements in the water, obtains movements, which alternate between a
movements in one direction and a movement in another direction that is
different from the first direction. The movements in the water can
comprise wave movements in the water or at the surface of the water,
alternating movements, i.e. alternating back and forth movements in the
water or at the surface of the water or generally movements alternating
between a movement in one direction and a movement in another direction
in the water of the pool of water. In the case of a buoy, floating at the
surface of the water in the pool of water, this can mean that the buoy,
at the up and down movements of the water surface, alternatingly rises
and sinks and/or alternately rocks or tilts back and forth. In general
then, the buoy has an average density lower than that of water. The other
device arranged at or in the pool of water may for example comprise a
body having the same density as or a higher density than that of water,
which is designed to follow the movements of the water, or a device that
is being alternately compressed and expanded due to pressure differences
in the water which occur when water waves pass. [0018]A driveshaft, which
is rotationally journalled at some part of the wave power plant. In
different designs, it can be journalled at the buoy or at the other
device. Alternatively it can be journalled for rotation at a device that
is rigidly attached to the bottom of the pool of water, or generally to
some device arranged to counteract the movements of the water in the pool
of water, such as a body having a relatively large mass or weight.
[0019]A first elongated means, which both is connected to a device
arranged to counteract the movements of the water in the pool of water,
for example a fixed point at the bottom of the pool of water or a body
having a relatively large mass or weight, or to the buoy, respectively,
depending on the place where the driveshaft is mounted, and is connected
to the driveshaft. The first elongated means may be a flexible means,
such as a line, wire or chain, but it can also be stiff, in that case for
example comprising a rack gearing segment. [0020]An electric generator
connected to the driveshaft and comprising two parts that are rotatable
in relation to each other, a first part and a second part, often called
rotor and stator, respectively. An air gap exists between the two
rotatable parts. [0021]An accumulation device for temporary mechanical
storage of energy as described above.

[0022]The buoy or the similar device is arranged and the buoy or the other
device, the first elongated means, the device arranged to counteract the
wave movements, the driveshaft and the energy accumulation device are
connected to each other, so that the connection between the first
elongated means and the driveshaft makes the driveshaft rotate,
substantially for first movements of the water surface or for first
movements of the buoy or the similar device, in only one direction,
thereby driving said two part of the electric generator to rotate in
relation to each other in a first direction and generate electricity and
at the same time also supply energy to the accumulation device. Thus,
energy from the rotation of the driveshaft is hereby partly converted to
electric energy, which is delivered from the electric generator, partly
to energy which is stored in the energy accumulation device. The first
movements can for a buoy be the movements into which the buoy is set by
either one of the up- or down-going movements of the water surface.

[0023]The energy accumulating device is arranged to drive, for
substantially second movements, that are substantially different from the
first movements, of the buoy or the similar device, said two parts of the
electric generator to rotate in the same first rotation direction in
relation to each drives said two parts of the electrical generator to
rotate in relation to each other. The second movements can for a buoy be
those movements, into which the buoy is set by second of the up and down
going movements and thus are substantially different from said either one
of the up and down going movements of the water surface.

[0024]The first movements of the buoy or the other body can take place in
a direction, which is mainly the opposite the direction, in which the
second movements of the buoy or the other device are made. Thus, the
first movements can take place in a forward direction whereas the second
movements take place in a backward direction, either as a translation
movements, for example up or down, or as a rotational motion, i.e.
angularly, or as a combined translation and rotational movement.

[0025]The driveshaft may be mechanically connected, for example via a
mechanical gear, to the first part of the electric generator. An
electromagnetic coupling exists in a conventional way over the air gap
between the first and second parts of the electric generator at least
when these parts are moving in relation to each other. The energy
accumulation device may in one special embodiment be mechanically
connected to the second part of the electric generator.

[0026]The connection of the energy accumulation device to the driveshaft
via the electromagnetic coupling over the air gap between the first and
second parts of the electric generator gives a motive force, which
counteracts to the rotation of the driveshaft when the driveshaft is
rotating, by the connection between the first elongated means and the
driveshaft, and thereby is driving the first part of the electric
generator. Then, in the above mentioned special embodiment, the second
part of the electric generator can rotate in a first direction due to the
coupling to the drive shaft through the electromagnetic coupling over the
air gap and the first part of the electric generator, when the motive
force which is acting on the driveshaft through the coupling between the
first elongated means and the driveshaft exceeds the counteracting motive
force, energy being accumulated in the energy accumulation device due the
mechanical coupling thereof to the second part of the electric generator.
At the same time, the first and second parts of the electric generator
are rotating in the same first direction in relation to each other.
Furthermore, the second part of the electric generator is driven by the
energy accumulation device to rotate in the same first direction
substantially when the motive force, which acts on the driveshaft through
the coupling between the first elongated means and the driveshaft, does
not exceed the counteracting motive force. Hereby, the first and second
parts of the electric generator are made to continue to rotate in the
same first direction in relation to each other also in this case.

[0027]As has been mentioned above, a mechanical gear may be arranged for
coupling the driveshaft to the first part of the electric generator. The
driveshaft is then suitably connected to an input side of the mechanical
gear and the first part of the electric generator is mechanically
connected to a first output side of the mechanical gear. In this case,
the second part of the electric generator can be rigidly attached to the
buoy, if the energy accumulation device is connected to a second output
side that is different from the first output side of the mechanical gear.
A mechanical gear can generally be regarded to comprise one input side
having an input shaft and two output sides, where one of the output sides
comprises an output shaft and another output side comprises a housing or
enclosure of the mechanical gear, also see the discussion below of only
the transmission included in the wave energy plant. For example a
planetary gear, the input side may comprise a shaft connected to the
planet gear carrier and the two output sides correspond to shafts
connected to the sun gear and ring gear, which may be connected to a
second shaft or the housing of the planetary gear.

[0028]In the case including a buoy, the buoy can comprise a space which
functions as an air pocket and in which at least the main part of the
driveshaft is mounted as well as other rotating parts, such as winding
drums, in the case where such are provided and couplings between them.
Such an air pocket can be a space filled with air, which at its bottom is
delimited by a water surface and the other sides of which are different
surfaces of the buoy. Then, the air pocket may be formed by a recess in
the bottom surface of the buoy.

[0029]The energy accumulation device can in one embodiment comprise a
counterweight, arranged as a lead, to also move upwards for said first
movements of the buoy or the other device, thereby increasing its
potential energy. The coupling of the buoy or the other device, the first
elongated means, the driveshaft and the counterweight to each other is
then suitably arranged so that the counterweight moves downwards, for
said second one of the movements of the buoy or the other device, thereby
driving the parts of the electric generator to rotate in relation to each
other in the first rotational direction. In the case of a buoy, this can
for example mean that, for the first movements, when the buoy e.g. is
moving upwards, the counterweight is also moving upwards a distance,
which is greater than the vertical distance in which the buoy then
vertically moves.

[0030]The energy accumulation device can in the same embodiments comprise
a counterweight drum which is rotationally mounted to the driveshaft and
a second elongated means for coupling movements of the counterweight to
make the counterweight drum rotate. The second elongated means can be
flexible or can be a flexible means such as a line, wire or chain, which
at a lower end is attached to the counterweight and at its upper end is
more or less wound around the counterweight drum. Furthermore, the
driveshaft is connected to drive the first part of the electrical
generator to rotate and the counterweight drum can in a first case be
coupled to rotate the second part of the electric generator, so that the
electric generator generates electric current when its second part is
rotated in relation to its first part and at the same time gives a torque
counteracting this rotation. Hereby, the first and second parts of the
electric generator can be made to always rotate always in the same first
direction in relation to each other.

[0031]In a second case a mechanical gear can be connected between the
driveshaft and the first part of the electrical generator. In this case
the driveshaft is connected to an input side of the mechanical gear, the
second part of the electric generator is rigidly attached to the buoy or
the other device and the counterweight drum is mechanically coupled to a
second output going side different from the first output side of the
mechanical gear. The driveshaft can hereby, for said first movements of
the buoy or the other device, provide motive forces on both of the output
sides of the gear, in order to rotate the first part of the electric
generator and to rotate the counterweight drum to elevate the
counterweight in relation to the driveshaft. The counterweight drum can,
for said second movements of the buoy or the other device, provide a
motive force, through its coupling to the second output side of the
gearbox, in order to rotate the first part of the electric generator.

[0032]Furthermore, in the case including a counterweight and a
counterweight drum, an electric cable for the electric connection of the
generator can be provided which extends from the generator to the
counterweight drum and is partly wound around it, which therefrom extends
to a non floatable part which is slidable along the first elongated means
and to which it is rigidly connected, so that the sliding part can be
maintained at a constant distance beneath the counterweight, and which
electric cable extends from the slidable part up to the water surface to
be further connected to an electric load. This may allow the wave energy
converter to turn in the horizontal plane, such as when the direction of
the water waves changes, without causing the electric cable to be
entangled with the first elongated means.

[0033]An anchor drum can be mounted for unidirectional rotation around the
driveshaft and further be coupled to the first oblong organ to make the
anchor drum rotate for the first ones of the movements of the buoy or the
other device, and thereby also making the driveshaft rotate. The first
elongated means can be flexible, i.e. be a flexible means such as a line,
wire or chain, which at one end is more or less wound around the anchor
drum. A mechanism can be provided for rotating, for the second movements
of the buoy or the other device, the anchor drum so that the flexible
organ is kept in a tensioned state. Hereby, in can also be counteracted
that the wave energy plant is moved away along the surface of the water.
The mechanism can for example comprise a mechanical coupling between the
energy accumulation device and the anchor drum or comprise an electric
motor.

[0034]The bearing for the anchor drum, which only allows a unidirectional
rotation around the driveshaft, at the same time allows the anchor drum,
when rotating in the opposite direction, to drive the driveshaft to
rotate in the opposite direction, which is the above said only one
direction. This bearing can comprise a coupling for limiting or
disengaging the motive force with which the anchor drum then acts on the
driveshaft.

[0035]A control system for controlling the electrical load of the electric
generator can be provided that is arranged to adapt the rotational speed
between the first and the second parts of the electric generator. In the
case where the energy accumulation device comprises a counterweight or a
floating body, control of the electrical load can also be used for adapt
the vertical speed of the counterweight or of the floating body,
respectively, whereby it also becomes possible for the counterweight or
the floating body, respectively, to only move within an adapted or
suitable vertical range. The control system can also be arranged to
compensate for variations in the torque, which is caused by the inertia
of the mass of the counterweight or the floating body, respectively, by
adjustment of the rotation speed between first and the second parts of
the electric generator. Hereby it can be achieved that the electric
generator is capable of supplying a continuous, even power.

[0036]The wave energy converter may have one or more of the following
characteristics and advantages: [0037]1. Accumulation of energy according
to the description above can be used for equalizing the energy of the
water waves and thereby generate electricity at an even level, which
gives a high capacity factor of the generator and associated power
electronic circuits and connections, and a low complexity of the electric
power system. [0038]2. Excess energy from large waves can be accumulated
and used over time to compensate for shortage in smaller waves, which
contributes to the high capacity factor. [0039]3. Absorption of energy
from the water waves can be limited while full power can be maintained
even during very heavy wave conditions. This contributes to the high
capacity factor, but it also works as a very simple and efficient storm
protection system where the wave energy plant all the time works in
harmony with the waves, only absorbing the amount of energy that it has a
capacity to convert. [0040]4. The power output of the generator can be
controlled by the fact that the rotation speed of the generator can be
adapted to the average rotation speed of the driveshaft. This brings
about that the wave energy plant can deliver an even power level in
relation to the current wave climate. [0041]5. The wave energy plant is
highly scalable and its capacity and pattern producing electric power can
be optimized for specific wave climates for the highest cost efficiency.
[0042]6. The wave energy plant has a completely mechanical transmission
having a high efficiency, which in simple way converts the oscillating
wave movements into a unidirectional rotation, well adapted to a standard
electric generator having a rotating rotor. [0043]7. The construction can
for example mainly be made from concrete, a cheap material which is well
tested for ocean environment. [0044]8. An electronically adjustable
sliding clutch may be used, which is arranged to influence the winding of
a line between a bottom foundation and the buoy and which also makes it
possible to adjust the force which is needed to maintain the horizontal
position of the wave energy plant. Such a sliding clutch may replace and
enhance the function of a counterweight, here called a lead, which is
often used in similar constructions.

[0045]9. An anchor drum, which is mechanically connected to the
driveshaft, can be used for more or less winding the second elongated
means, according to the wave movements. Several revolutions of the anchor
line can be wound around the anchor drum and hence it has no technical
limitations for wave heights that the installation can handle. The buoy
follows the surface of the water in a harmonic way for all wave sizes
without reaching any end position, which contributes to the fact that the
wave energy plant can very efficiently absorb wave energy, in spite of
varying wave heights and at the same time the strain on the construction
during storm conditions is minimized. [0046]10. Mechanical couplings may
be provided, so that if the electrical generator is supplied with
electric energy from an external source and acts as an electrical motor,
the anchor drum can be controlled to move to perform a controlled winding
of the line. This can confer to the wave energy plant the property that
it can be assembled on shore before it is towed to the installation site
thereof. [0047]11. The installation can be done with a minimum of manual
assistance. It is mainly only an electric cable that has to be manually
connected, which can be done at the surface of the water from a boat. A
bottom foundation, which is connected to the second elongated means, and
the counterweight are attached to the buoy during transport to the
installation site and then they can be released by control of mechanic
couplings/locking devices. [0048]12. The wave energy converter can easily
be designed to be suitable for different installation depths. [0049]13. A
gearbox can be used to increase the rotation speed of the electrical
generator, this allowing the use of a smaller and more resource efficient
high speed generator. Such a gearbox can also make it possible to
permanently fix the second part of the electric generator, the stator, to
the buoy, by connecting the gearbox to the counterweight drum, which can
simplify the electrical connection and encapsulation of the generator and
reduce the rotating mass in the construction.

[0050]Generally, as described above, a method of extracting electric
energy from more or less periodic movement of a body, such as repeated
upward and downward movements and/or tilting movements in two opposite
directions can comprise the following steps. [0051]For first movements of
the body, these movements can drive two parts of an electric generator to
rotate in relation to each other in a first direction and thereby
generate electric current and at the same time provide mechanical energy
to an energy accumulation device. [0052]For second movements of the body,
which are substantially different from the first movements, the energy
accumulation device can drive the two parts of the electrical generator
to rotate in the same first direction in relation to each other and
thereby generate electric current having the same polarity as during the
first movements of the body.

[0053]The transmission used in the wave energy converter as described
above can independently be used in other cases of power generation, where
a driveshaft is driven intermittently, with changing directions and/or
with varying speeds and/or torques. Generally, the transmission then
comprises a driveshaft that is arranged to be driven and that by some
suitable device, if required, always can be made to rotate in one
rotational direction. Furthermore, an electrical generator coupled to
driveshaft is provided, which generator comprises two parts that can
rotate in relation to each other, and an energy accumulation device. The
driveshaft drives the two parts of the generator to rotate in relation to
each other in a first direction and thereby generate electric current.
The energy accumulation device is coupled with the driveshaft and the
electric generator, so that the driveshaft by its rotation can also
supply energy to the energy accumulation device and so that the energy
accumulation device can later deliver its stored or accumulated energy to
cooperate in driving the parts of the generator to rotate in the same
first direction in relation to each other. Thereby, electric current can
be generated having the same polarity, when the rotational speed and/or
the torque of the driveshaft is/are insufficient to drive the parts of
the generator to rotate at a maintained rotational speed.

[0054]In the transmission, the driveshaft can be mechanically connected to
the first one of the parts of the electrical generator. In the generator
there is, as conventionally, an electromagnetic coupling over an air gap
between the first and the second part, at least during their movements in
relation to each other, which the coupling gives some torque between the
two parts. The energy accumulation device can in a first case be
mechanically coupled to the second part included in the electrical
generator.

[0055]Furthermore, in the transmission a gearbox, e.g. a planetary
gearbox, can as described above be connected between the driveshaft and
the generator, so that the driveshaft is mechanically connected to the
input side of the gearbox or generally to a first rotational part of the
gearbox. An output side of the gearbox or generally a second rotational
part of the gearbox is then arranged to be driven from the outside to
rotate with a varying rotational speed and/or torque in one rotational
direction. One of the two parts of the electrical generator is
mechanically coupled to another output side of the gearbox, generally a
third rotational part of the gearbox, and the energy accumulation device
is mechanically coupled to the second part of the generator. The first
and second rotational parts of the gearbox can then cooperate to for
example drive the third rotational part of the gearbox to rotate with a
rotational speed higher than the rotational speeds that each of the parts
by itself can achieve when the other of these parts stands still or is
not driven.

[0056]The gearbox should in any case have the following functions:
[0057]When the first rotational part is driven from the outside, the
second and the third rotational parts are also made to rotate. [0058]When
the first rotational part is not rotating, the third rotational part can
drive the second rotational part to rotate.

[0059]The first, second and third rotational parts can also be arranged to
rotate around the same geometric rotational axis, i.e. be coaxially
mounted.

[0060]Additional objects and advantages of the invention will be set forth
in the description which follows, and in part will be obvious from the
description, or may be learned by practice of the invention. The objects
and advantages of the invention may be realized and obtained by means of
the methods, processes, instrumentalities and combinations particularly
pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061]While the novel features of the invention are set forth with
particularly in the appended claims, a complete understanding of the
invention, both as to organization and content, and of the above and
other features thereof may be gained from and the invention will be
better appreciated from a consideration of the following detailed
description of non-limiting embodiments presented hereinbelow with
reference to the accompanying drawings, in which:

[0062]FIG. 1 is a schematic image of a wave power installation comprising
four separate wave energy plants,

[0063]FIG. 2a is a side view of a wave energy converter including a
counterweight,

[0109]FIG. 14 is a bottom view of a power train including only one
generator mounted in a buoy,

[0110]FIG. 15a is a front view of a wave energy plant having an
alternative design of a power train including only one generator, the
stator of which rotates together with the counterweight drum, one
counterweight and an alternative guide mechanism for an anchor line,

[0111]FIG. 15b is a side view of the wave energy plant of to FIG. 15a,

[0112]FIG. 15c is a front view of a wave energy plant of FIG. 15a having a
different type of divided anchor line,

[0118]FIG. 15i is a view similar to FIG. 15g, in which a return feed
mechanism in the power train is driven by an electric motor,

[0119]FIG. 16a is a diagram illustrating a control rule for compensating
for varying accelerations and decelerations of the counterweight using
the load of the generator,

[0120]FIG. 16b is a diagram illustrating a control rule for compensating
for varying accelerations and decelerations of the counterweight using a
CVT, and

[0121]FIG. 16c is a diagram illustrating a control rule for compensating
for varying accelerations and decelerations of the counterweight using
the sliding clutch of the return feed mechanism.

DETAILED DESCRIPTION

[0122]In FIG. 1, a wave power installation is shown for extraction of
energy from the movements of waves at a water surface 6 of a pool of
water, e.g. movements of water in a ocean. The wave power installation
comprises one or more wave energy plants 1, each including a buoy or a
floating body 3, which is located at the water surface, e.g. floating
thereon, and which to a higher or lower degree follows the movements of
the waves. In the upwards and downwards movements of the water surface 6
the buoy is made to alternating raise or sink and/or alternating tilt
back and forth. Thereby a motive force can be created, in the case shown
in relation to the bottom 8 of the water pool, such as a part rigidly
attached to the bottom, e.g. a bottom foundation 5, which can have a mass
large enough to keep it steadily on the bottom. If required, the bottom
foundation can of course be attached to the bottom in some way and it may
then comprise a simple fastening device having a low mass, not shown. As
can be better seen in FIGS. 2a and 2b the buoy 3 and the bottom
foundation--alternatively the bottom fastening device--are connected to
each other by an anchor line 7, e.g. a steel wire. The motive force can
as an alternative be created in relation to some kind of movable object
such as to a weight suspended in the buoy, see FIG. 7d.

[0123]In the shown embodiment the anchor line 7 is at one end attached to
the foundation 5 and is at its opposite end attached to a power train 2
and more or less wound around a first winding drum, an anchor drum 9,
included in the power train, the winding drum being mounted to rotate
about a driveshaft 11. The driveshaft 11 is in a suitable way journalled
at the buoy 3. As shown in FIGS. 2a and 2b the buoy can at its bottom
side comprise downwards protruding stays 13, which can be said to
constitute a frame and at which the driveshaft 11 is journalled, e.g. at
its two ends. On the driveshaft, in the embodiment shown in these
figures, there is also a second winding drum, a counterweight drum 15, on
which a line 17 is partly wound at its upper end. The counterweight line
7 carries at its lower end a counterweight 19. The cylindrical surface of
the counterweight drum, on which the line for the counterweight is wound,
has in the shown embodiment a diameter that is larger than that of the
cylindrical surface of the anchor drum 9, on which the anchor line 7 from
the bottom foundation 5 is wound. The first mentioned diameter can e.g.
be considerably larger than the latter one, such as a relation in the
magnitude of order of 2:1 to 3:1, but does not have to. The winding drums
can also have the same diameter when suitable.

[0124]Instead of having the power train 2 mounted under the buoy 3, as
shown in FIGS. 2a and 2b, the power train can be mounted in a recess in
the buoy, a power train room 20, as shown in FIGS. 2c, 2d and 2e. Then,
the driveshaft 11 can be mounted in a substantially central position in
the buoy. The stays 13 can be attached to walls of the power train room
20.

[0125]Thus, the anchor line 7 and the counterweight 19 are not directly
connected to each other as in earlier known constructions. In the earlier
known constructions, see the principle picture of FIG. 11a, half the
motive force of the buoy 3 is accumulated in the rise of the wave by
while the anchor line 7 running over the anchor drum 9', so that a
generator 21 for generating electric current can be driven also when the
wave thereafter sinks. In the latter case, the generator is either driven
in a reverse direction or the rotation movement is rectified by a
mechanical or hydraulic transmission solution, not shown. However, in
both cases the generator 21 remains to be direct driven according to the
momentary vertical movement of the wave.

[0126]As appears from FIGS. 11b and 11c the generator can instead be
connected to be driven between the counterweight 19 and the anchor drum
9, so that e.g. a first part of the generator, not shown in these
figures, typically corresponding the inner rotating part, the rotor, of a
conventionally mounted generator, on one side of the air gap of the
generator, not shown, is mechanically connected to the anchor drum and a
second part of the generator, not shown in these figures, typically
corresponding to the outer stationary part of the generator, the stator,
in a conventionally mounted generator, on the other side of the air gap,
is mechanically connected to the movements of the counterweight, so that
this part can also rotate. Hereby the generator 21 can be driven from two
sides with a maintained relative rotational direction between its first
part and its second part. When the wave and the buoy 3 raises, the
driveshaft 11 is turned forwards by the anchor line 7, which runs around
the driveshaft via the anchor drum 9 and which at its other end is
anchored to the bottom 8, e.g. to a foundation 5. The counterweight 19 is
used to create a resilient resisting force and thereby gives an even
torque between the counterweight drum 15 and the driveshaft 11, which in
that way drives the first part and second part of the generator in
relation to each other. It is also possible to use other methods to
achieve such a driving operation, e.g. gas pressure or a spring for
providing a constant force, as will be described below.

[0127]In FIGS. 11a, 11b, and 11c the arrows 111 show absorption of wave
energy. The absorption level varies according to the momentary movement
and movement direction of the wave. When the driveshaft 11 is turned
forwards by the anchor drum 9, also the generator 21 follows the
rotation, so that the counterweight line 17 starts to be wound around the
counter weight drum 15, which can be a part of or be rigidly attached to
the second part of the generator, see the arrows 113, and so that the
counterweight is moved upwards. Hereby, potential energy is stored in the
counterweight at the same time as a torque appears over the generator
(torque=weight of the counterweight*acceleration of gravity (i.e. the
gravitational force acting on the counterweight)*radius of the
counterweight drum). The torque makes the second part of the generator
start rotating in relation to the first part, which is mechanically
connected to the driveshaft 11, so that the counterweight line 17 starts
to unwind from the counterweight drum 15, and hereby potential energy
accumulated in the counterweight 19 is converted to electricity, see the
arrows 115. The faster the generator parts rotate in relation to each
other, the more electric power is generated, and then also a higher
counteracting force is obtained in the generator 21, i.e. the
electromagnetic coupling between the two parts of the generator becomes
stronger. When the counterweight 19 reaches a certain velocity, the
pulling force from the counterweight becomes equal to the counteracting
force in the generator, this resulting in that the rotation speed of the
generator and the power output from the generator is stabilized in an
equilibrium state.

[0128]This way of connecting and driving the generator 21 can give great
advantages, since the generator can be used much more efficiently
compared to what have been earlier possible. The same relative rotational
direction between the generator parts is maintained all the time and the
generated electric power is kept at a substantially even level, which
requires a minimum of subsequent electric treatment of the electrical
voltage generated by the generator. The arrangement of the generator can
also give advantages from a storm safety point of view, since the motive
force over the generator and transmission is limited.

[0129]The design of the transmission unit 2 and the function thereof will
now be described in more detail with reference in particular to FIGS. 2a,
2b and 3a.

[0130]During the movements of the waves the distance between the buoy 3
and the bottom foundation/bottom fastening device varies. The anchor drum
9 is turned, due to the coupling with the anchor line 7, in a first
direction when the water surface 6 rises, and is then locked to the
driveshaft 11, which thereby is rotated by the anchor drum. When the
water surface at the buoy sinks, the driveshaft is locked from rotating
backwards in the opposite direction by anti-reverse mechanisms 53 in the
shaft stays 13, see FIGS. 5a and 5b. To be capable of turning the anchor
drum backwards, in a second, opposite direction, and to keep the anchor
line in a tensed state when the water level 6 at the buoy 3 sinks, a
return feed mechanism of some kind sort is required as will be described
below. The driveshaft 11 is in turn connected to the generator 21. The
coupling between the driveshaft and the generator can be fixed or it can
as illustrated comprise a mechanical gear 23, which e.g. has a fixed
teeth relation or fixed gear ratio, and which gears up the rotation speed
of the generator. Hereby one of the parts of generator that are rotatable
in relation to each other, here for the sake of simplicity called rotor
and stator, e.g. an inner generator rotor 21', compare FIG. 3a, to rotate
in the first direction. The other rotatable part of the generator, e.g.
an outer stator 21'' is rigidly mounted to the counterweight drum 15. The
generator parts are separated by an air gap 21'''.

[0131]Due to the winding of the counterweight line 17 around the
counterweight drum 15 during the forward feeding of the driveshaft 11, a
relatively constant motive force or a relatively constant torque acting
on the driveshaft 11 is achieved, which through the connection between
the rotor 21' and the stator 21'' of the generator 21 drives the
generator to rotate and generate electric current. When the torque from
the anchor drum 9 exceeds the counteracting torque, that is derived from
the electromagnetic coupling over the air gap between the rotor and the
stator of the generator, when these parts are rotating in relation to
each other, more of the counterweight line 17 is wound around the
counterweight drum 15 and the excess energy, to which this higher torque
corresponds, is accordingly accumulated the hoistening of the
counterweight 19. Thereafter, when the buoy 3 starts to rise with a
decreasing speed, to thereupon sink when the water surface 6 sinks, also
the rotational speed of the driveshaft 11 and the rotor 21' in the first
rotational direction is also reduced. When the torque from the anchor
drum 9 becomes lower than the counteracting torque in the generator 21
according to the discussion above, the counterweight line 17 starts to
unwind from the counterweight drum at an increasing speed, until of the
driveshaft is blocked from rotating in the reverse direction by an
anti-reverse mechanism 53 in the driveshaft stay 13, see FIGS. 5a and 5b,
and the speed of the backward rotation of the counterweight drum is
stabilized by the equilibrium state between the generator and the
counterweight 19. The potential energy accumulated in the counterweight
hence continues to drive the generator 21 also in this phase, with a
correspondingly even torque as in the previous phase.

[0132]As has been mentioned above, the wave energy is absorbed from the
traction force that arises between the buoy 3 and the bottom
foundation/bottom fastening device 3 during the rise of the wave. The
buoy 3 follows the movements of the wave and thereby moves the driveshaft
11, on which the anchor drum 9 is mounted, upwards in relation to the
bottom foundation. A rotational movement arises which drives the
transmission. The vertical movement of the wave is converted into a
rotational movement, the speed of which can then be geared up to be
suitable for driving the generator 21. It is the speed of the vertical
movement of the wave that determines the amount of energy that can be
extracted. The bigger wave, the faster vertical movement and the more
energy can be absorbed. Different from the energy in the wave, the
vertical speed of the movement does not increase with the square of the
wave height, but follows a more linear pattern. But the larger the wave
is, the less impact has the attenuating effect of the buoy 3, this
resulting in that the vertical movement and the motive force of the buoy
rapidly increase when the wave height increases from a low level to level
out towards the linear pattern the higher the wave becomes.

[0133]The anchor drum 9 is in a suitable way mechanically connected to the
drive shaft 11. Such a mechanical coupling can include the following two
functions. [0134]1. During the rise of the wave the anchor drum 9 shall
hook on to the drive shaft 11, so that the driveshaft is rotated together
with the rotational movement of the anchor drum. When the wave sinks, it
shall be possible to disengage the anchor drum, so that the anchor drum
can be rotated in the reverse direction. Furthermore, the driveshaft 11
shall be blocked from changing its rotational direction when the wave
sinks. The drive shaft is in this manner fed forward by the anchor drum
in the same rotational direction every time the wave rises and the motive
force, and thereby rectifies the motive force absorbed from the wave
motions. This makes it possible to drive the generator in a single
rotational direction. [0135]2. The absorption of wave energy can be
limited by the use of a sliding clutch 55, which consequently can word as
an overload protection, see FIGS. 5a, 5b and 5c. Such a sliding clutch
also makes it possible to completely disengage the absorption of energy
from the movements of the waves, by letting the anchor drum 9 slide
against the driveshaft 11 during the rise of the wave, when the
accumulation level reaches its upper limit, i.e. when it is not possible
to wind more of the counterweight line 17 around the counterweight drum
15 without risking that the counterweight 19 comes to close to and
damages the counterweight drum 15 and the buoy 3. The sliding clutch can
also be used to limit the torque to which the transmission is submitted.
When the wave sinks, the buoy 3 and the counterweight 19 will be
retarded, which gives an increased g-force and hence an increased torque
in the transmission. When the wave turns and rises again, the g-force
will increase further by the anchor drum 9 starting to be turned forward
and lifting the counterweight in relation to the buoy at the same time as
the buoy is lifted by the wave. For a too high load the sliding clutch
slides and thereby somewhat reduces the acceleration, which in turn also
reduces the torque to which the transmission is submitted.

[0136]A mechanical coupling between the anchor drum 9 and the driveshaft
11, which provides these functions, can be designed in different ways.
Such a coupling can comprise one or more anti-reverse mechanisms and a
sliding clutch as will be described below.

[0137]Thus a freewheel mechanism or an anti-reverse mechanism 51, see FIG.
5a, for the coupling of the driveshaft 11 to the anchor drum can be
provided, which is herein called the anti-reverse mechanism of the anchor
drum. In this case, the driveshaft passes through the anchor drum
undivided. The anti-reverse mechanism 51 of the anchor drum can be
designed like a one way bearing, which is mounted around the driveshaft.
When the buoy 3 rises, the anchor drum 9 and the driveshaft 11 is turned,
as above, in the first rotational direction, by way of the anchor drum
hooking on to the driveshaft with the use of this return blocking
mechanism 51. When the buoy 3 sinks, the return blocking mechanism in the
anchor drum 9 is released and the anchor drum 9 can be reversed, rotated
in the opposite rotational direction, to wind up the anchor line 7, such
as will be described below, meanwhile the driveshaft 11 is blocked from
rotating in the opposite rotational direction by another return blocking
mechanism 53, which is acting between the driveshaft and the stay 13 and
which is here called the shaft stay return blocking mechanism 53. This
return blocking mechanism can be arranged at or in the stay bearing 54
for the driveshaft 11. In this way the driveshaft is always turned in the
first rotation direction every time the buoy 3 rises and it can never be
turned in the opposite direction.

[0138]If so is required, the transmission unit 2 can be designed, so that
motive force, with which the anchor drum 9 acts on the driveshaft 11, can
be disengaged also in the first rotational direction. This can be
achieved by a controllable return blocking mechanism 51 of the anchor
drum, or preferably with the use of a sliding clutch 55 for the anchor
drum, as will be described below. The drive of the driveshaft 11 can then
be disengaged, when the accumulation of energy reaches its maximum
accumulation level, i.e. when the counter-weight 19 cannot be hoisted up
any higher without the risk of damaging the anchor drum 15 and/or the
buoy 9. This disengagement of the drive of the driveshaft is then ended,
when the buoy 3 starts sinking, so that the anchor drum 9 drives the
driveshaft 11 anew when the wave starts rising again. The energy
absorption of the wave energy converter is hereby limited and overload of
the transmission and the generator 21 can be prevented, when the average
wave height exceeds the level, at which the wave energy converter reaches
its maximum capacity, i.e. rated power. Even though the energy absorption
is hereby temporarily disengaged, the generator can be driven to produce
maximum power output, as long as the potential energy stored in the
counterweight can be used. The load on the generator 21 and the
transmission 23 can hereby be limited at the same time as maximum power
output can be maintained, as soon as the average energy level in the
waves is high enough.

[0139]An alternative method for disengagement of the driveshaft 11 from
the anchor drum 9, to limit the energy absorption, is that both
engagement and disengagement is done when the torque, which is
transferred between the anchor drum and the driveshaft, is zero. In this
case a claw coupling 55'' can be used instead of a sliding clutch, see
FIGS. 5e and 5f. When the counterweight 19 has exceeded an upper limit,
the claw coupling is disengaged as soon as the torque has been reduced to
zero, see FIG. 5f. The claw coupling is engaged again, see FIG. 5e, when
the counterweight has reached a certain lower limit, and when the torque
is zero again, which may be several wave periods later. The upper limit,
as above, must provide enough safety margins so that the counterweight 19
doesn't reach the counterweight drum 15 even if an extreme wave comes.
Advantages with this method includes that the disengagement mechanism can
manage a higher torque being transferred, low energy consumption only
during transition, and minimum of mechanical wear from the disengagement.
The disadvantage is that a longer counterweight line 17 is required,
which can be limiting in some cases.

[0140]The anchor drum's 9 sliding clutch 55 can be mounted between the
anchor drum's return blocking mechanism 51 and the anchor drum, as
schematically shown in FIG. 5a. The by the sliding clutch transferred
torque between the anchor drum and the drive shaft 11 can preferably be
controllable in accordance with some suitable electrical signal, by which
the maximum energy absorption level in the system can be adjusted.

[0141]In an alternative design the mechanical return blocking mechanism of
the anchor drum 51, does not exist, see FIG. 5b. The driveshaft 11 is
also in this case passing through the anchor drum 9 undivided. Instead
the anchor drum's sliding clutch 55 is used as a return blocking
mechanism. The sliding clutch is mounted around the drive shaft 11 with
one of its coupling sides and mounted to the anchor drum 9 with its other
coupling side. The torque transfer in the sliding clutch 55 is controlled
to also give the function of a return blocking mechanism.

[0142]In yet another alternative design there is a detached sliding clutch
55' without mechanical return blocking mechanism, see FIG. 5c. The
driveshaft 11 is in this case divided and the anchor drum 9 is firmly
attached to the first part of the driveshaft 11'. There is a sliding
clutch 55' between the first part 11' and its second part 11'' of the
driveshaft, to the side of the anchor drum. The first part of the shaft
11' is journalled in bearing to an inner stay 13' between the anchor drum
and the sliding clutch at bearing 54'. The sliding clutch 55' is, as
above, used as a return blocking mechanism and its torque transfer is
controlled in the same way as when the sliding clutch is enclosed in the
anchor drum 9.

[0143]When the sliding clutch 55, 55' is used as a return blocking
mechanism, it can be controlled as visualized in FIG. 5d. It then
alternates between transferring full torque and no torque at all. The
anchor drum 9 rotates forward, meanwhile the wave is rising, and is then
fed backwards by the below described return feeding mechanism, when the
wave is sinking. The alternation in torque transfer hence occurs when the
rotational direction of the anchor drum is turned.

[0144]The rotation of the anchor drum 9 and the rotation of the
counterweight drum 15 can also be coupled via a mechanical coupling, the
above mentioned return feeding mechanism, beside with the help of the
electromagnetic coupling through the generator 21. This can be achieved
with help of, among other things, a second sliding clutch 25, here called
the return feeding sliding clutch, see FIG. 6, which is used for
controlling the level of torque, which shall be transferred from the
counterweight drum to the anchor drum. The level of this torque can also
be adjustable or dirigible. This torque can be used to reverse the anchor
drum 9 and by that secure that the anchor line 7 to the bottom foundation
5 is kept in a tensed state, meanwhile the buoy 3 sinks. This torque can
also be used for counteracting the driftage of the buoy, away from the
sea floor foundation, due to currents and wind at the water surface 6.

[0145]The return feeding sliding clutch 25 can as shown be mounted in one
of the stays 13, in which the driveshaft 11 is journalled in bearings.
Gearwheel 27, 29 runs against the edges 31, 33 on the wind up drums 9 and
15 respectively and these edges can then in the corresponding way be
toothed. The gearwheels 27 and 29 is connected to the input- and
output-shafts of the sliding clutch 25 and their size in relation to the
gearwheels 31, 33 at each wind up drum respectively, is adapted to
provide high enough gear ratio for the rotation speed of the anchor drum
9 to be high enough to wind up the anchor line 7 fast enough to keep it
tense, when the floating body 3 sinks as fastest. In the shown design the
gearwheels 27, 29 is coaxially journalled in bearings and directly
connected to the two clutch disks 57 in the return feeding sliding clutch
25, which are pressed against each other with a controllable force, so
that when so is required, a torque of desirable magnitude can be
transferred between the counterweight drum 15 and the anchor drum 9. One
alternative return feeding mechanism for the anchor drum is to use an
electrical motor in a corresponding way as shown in FIG. 15i.

[0146]The gear 23, that connects the driveshaft 11 to the generator 21,
can give a stepped up rotational speed of the driveshaft so that a higher
rotational speed in the generator is obtained, which enables the use of a
high speed generator. Since the power output from the generator is
proportional to the mass of its rotor 21' and its stator 21'' and to the
rotational speed of the generator, this is of very high importance.
Further on, the gear 23 can in general be or comprise a variable gear,
where it can comprise e.g. a gear with fixed gear ratio such as a
planetary gear 35, arranged as input stage, see FIG. 12e. The outgoing
shaft of the planetary gear is then connected to the input shaft of a
variable gear 37 (CVT), of which output shaft is connected to the first
of the generator's part, like its rotor 21'. The generator stator 21'',
and the casing of these gears is fixed to each other and the
counterweight drum 15 and can rotate freely as one unit around the
driveshaft 11. The gear ratio between the driveshaft 11 and the first
part of the generator 21' is in this case given by the product of the
gear ratio of the planetary gear 35 and the gear ratio of the variable
gear 37.

[0147]The maximum rotational speed, that the generator 21 can handle,
depends on the choice of generator. A suitable range for the generator's
nominal rotational speed is around 1500 to 3000 rpm depending on its
maximum capacity, for which the wave energy converter 1 is dimensioned.
To gear up the generator to such a rotational speed a gear ratio in the
magnitude of 100 to 200 times is required, where the gear ratio also
depends on the radius of the anchor drum and the medium motion speed of
the buoy where full power shall be reached. When the rotational speed is
stepped up, the torque is at the same time stepped down with the same
gear ratio, which brings a very high input torques in the gear 23. A high
gear ratio can cause high transmission losses. A planetary gear 35 as
above provides a high fixed gear ratio, can manage very high input
torques and has a good efficiency. The variable gear stage in the gear 37
can be used to adapt the generator's revolution speed to the actual
medium wave height. Such a variable gear can e.g. be a step less variable
gearbox or a hydraulic gearbox.

[0148]Alternatively, the transmission unit 2 can be designed with other
mechanisms for accumulation of energy from the rise of the water surface
6, e.g. as elastically stored energy. Any counterweight is then not
required, and can instead be replaced by a spring, typically a coil
spring 69, see FIG. 3b. The inner end of such a coil spring is then
mounted to the stay 13, while its outer end is mounted to the casing of
the gear 23 and is thereby coupled with the generator 21, to its second
part. Energy can also be accumulated as gas pressure which will be
described below.

[0149]In the so far described designs, one single anchor drum 9 and two
counterweight drums 15 located on either side of the anchor drum can
exist, as shown in the corresponding figures. One gear unit 23 and one
generator 21 is included in each counterweight drum. One counterweight
drum 15 is hence connected to either end of the driveshaft 11, i.e. the
driveshaft is mounted between the two counterweight drums and the
driveshaft is journalled in bearings in the stay or the frame 13.

[0150]The movements of the two counterweight drums 15 can be synchronized
with the use of a link shaft 58, that is journalled in bearings in the
stay 13 parts and has gearwheels 29 at both its ends, which concurs with
the toothed edges of the counterweight flanges 33, see FIG. 2f. The
generator arrangements 21 are freestanding but the counterweight 19 must
be kept on the same horizontal level so that the distance between the
counterweight and the anchor drum is the same in both arrangements.
Otherwise the centre of gravity in the wave energy converter 1 can be
displaced, so that the power unit can turn in a faulty manner against the
waves, with deteriorated capture ratio between the waves and the buoy 3
as a consequence. The link shaft 58 is in the showed design also used for
achieving the return feeding mechanism from the counterweight drums 15 to
the anchor drum 9. For this it also has a gearwheel 27, which concurs
with a ring gear on one of the anchor drums flanges 33 in a similar way
as for the return feeding mechanism shown in FIG. 6.

[0151]The motion of the two counterweight drums 15 can be synchronized
thanks to a link shaft 58 which is journalled in bearings in the stay 13
parts and has gearwheels 29 at both ends, which concur with gear rings on
the counterweight drums' flanges 33, see FIG. 2f. The generator
arrangements 21 are freestanding but the counterweights 19 must be kept
on the same horizontal level, so that the distance between the
counterweight and anchor drum is the same in both arrangements. In other
case the wave energy converter's 1 centre of gravity may be displaced, so
that the wave energy converter can turn incorrectly towards the waves
with decreased power transfer between the wave and the buoy as a
consequence. The link shaft 58 is in the presented design also used for
achieving the return feeding from the counterweight drums 15 to the
anchor drum 9. For this purpose it also has a gearwheel 27, which concur
with a gear ring on one of the anchor drum's flanges 33 in a similar way
as for the in FIG. 6 presented return feeding mechanism.

[0152]Since the link shaft 58 is made in one piece, to be able to rigidly
connect the rotational motion of the counterweight drums 15, another type
of sliding clutch for the return feeding mechanism must be used. The
sliding clutch of the return feeding mechanism 25' is in this case
located between the larger gearwheels 27, which concurs with the flanges
31 of the anchor drums 9, and the through going link shaft 58, at which
the gearwheels are fixedly mounted. Instead of driving with the help of
concurring gearwheels as shown in the figures, a belt-drive or
chain-drive can for example be used.

[0153]The stay 13 includes in the designs in accordance with FIGS. 2a-2b
two from the buoy's 3 underside protruding stay parts, each of which
includes a bearing 54 with a return blocking mechanism 53 for the
driveshaft 11, also compare FIGS. 5a and 5b. Such a design of the
transmission unit 2 with an along the driveshaft centralized anchor drum
9 and on both sides of this arranged counterweight drums 15 with
belonging gear 23 and generator 21, gives a symmetrical weight load on
the buoy and also a more symmetrical load due to currents in the water
compared to the case where only one counterweight drum with belonging
generator and counterweight 19 is used, which is connected to one end of
the driveshaft 11.

[0154]The transmission unit 2 with the anchor drum 9, the driveshaft 11,
the counterweight drums 15, the gear mechanisms 23 and the generators 21,
can as an alternative be carried in a machine body or in a driveshaft
frame 141, as shown in FIG. 2g. The machine body includes a surrounding
frame shaped part 143 and a number of shaft stays 145, which runs between
the long, opposite sides of the frame part and which corresponds to the
above described stays or stay parts 13. The shafts of the transmission
unit are journalled in bearings in the shaft stays. The number of shaft
stays is dependent on different design alternatives. The frame 141 is
secured to the buoy.

[0155]In the case where a planetary gear 35 is used, a somewhat different
design is possible. A planetary gear is composed by a planet carrier 161,
at which a number of planet gears 163 are journalled in bearings in an
orbit on the inside of a ring gear 165 and around a sun gear 167, at
which the planet gears are in gear wheel engagement, see FIG. 12a. When
the planet carrier rotates and the outer wheel, the ring gear, is fixed,
the planet holder drives the inner wheel, the sun gear, to rotate, which
steps up the rotation speed? Alternatively the sun gear 167 can be driven
by the rotation of the ring gear 165 while the planet holder 161 is held
in a fixed position, which also steps up the rotation speed. As above,
this can be utilized, so that the planetary gear 35 and the generator 21
e.g. is located inside the counterweight drum 15 and at first hand so
that both the planetary gear's ring gear 165 and the generator 21'' are
fixed to the counterweight drum, compare e.g. FIG. 2b.

[0156]Alternatively only the planetary gear 35 can be located inside the
counterweight drum 15 with the ring gear 165 fixed with the counterweight
drum. The generator stator 21'' is then instead fixed to the buoy 3 as
with the frame 141, see FIG. 2g and also FIG. 3d. The drive shaft 11 is
journalled in bearings and can rotate freely both at the entrance and
exit of the counterweight drum. The shaft load, which is given by the
counterweight 19, is taken up by the driveshaft, which is carried by the
shaft stay 145 in the driveshaft frame 141. The planetary gear 35 thereby
gets a low shaft load. The system function remains the same but such a
design can simplify the electrical connection and encapsulation of the
generator 21 and also simplify the access at service and maintenance. The
levy in mass can also be reduced, i.e. the total angular momentum, since
the stator 21'' in this case doesn't need to be rotated, which can be of
some significance. Also other types of gearboxes can be used in a similar
way, at which e.g. the casing or the cover of the gearbox is fixed with
the counterweight drum 15. A planetary gear's ring gear in this case
corresponds to the gearbox's house or casing.

[0157]The gear ratio in a planetary gear is given by the difference
between the number of teeth on the planet gear and the sun gear. In FIG.
12a a planetary gear is shown with one gear steps but it is possible to
build in additional gear steps. This can then be according to the
principle that two or more planetary gears are coupled with the ring
gears fixed to each other. Up to three steps are commonly used which
gives relatively low transmission losses. Every step is usually chosen
with a gear ratio between 5 and 10, which gives a gear ratio up to 300
with three steps. The higher power the wave energy converter 1 is
dimensioned for, the larger diameter the anchor drum 9 needs to have,
since the anchor line 7 requires a larger diameter at larger dimensions.
An increased diameter of the anchor drum leads to lower rotation speed in
relation to the vertical motion of the wave, which leads to that a wave
energy converter with larger capacity require a higher gear ratio to
achieve the correspondent rotation speed in the generator 21.

[0158]In FIGS. 11d and 11e is in the same way as in FIGS. 11b and 11c
schematically presented how the drive of the generator 21 can be achieved
for a generator with a with the buoy 3 fixed stator.

[0159]The buoy 3 will at the wave motions apart from moving vertically
also always change its angular orientation around a horizontal position,
which is taken at a completely calm sea. The driveshaft 11 then rocks
sideways all the time, which can get the anchor line 7 and the
counterweight line/lines 17 to slide and rub against each other on the
anchor drum 9 and the counterweight drum/drums 15. A track guiding
mechanism can then be used, which see to it that resp. lines are winded
up in a regularly way. One possibility is to use helicoidal grooves 39,
41, 43, 45 on the drums' 9, 15 cylindrical winding up surfaces, see FIG.
3c. When two counterweight drums are utilized, the direction of their
helicoidal grooves can be opposite, i.e. one of the helicoidal grooves
39, 41 is right handed while the other helicoidal grooves 43, 45 is left
handed, to maintain a symmetrical load on the wave energy converter 1,
due to the motive force relating to the counterweights 19 and the anchor
line 7, to some extent. Helicoidal grooves according to 39, 41, 43 and 45
with a shape that follows the profile of the lines can also significantly
increase the length of life of the lines since the contact surface
between line resp. the wind up drum is increased.

[0160]If only one anchor line 7 is used, the point where this line affects
the anchor drum 9 is moved along the axis, when the line is more or less
is winded up and unwound. To achieve a more symmetrical load in the case
with two counterweight drums 15 the anchor line 7' can be in a loop, so
that it runs from one side of the anchor drum at helicoidal groove 41,
down to the sea-floor foundation 5 and via a pulley 40, which is
journalled in bearing to the sea-floor foundation 5, and back up again to
the other side of the anchor drum via helicoidal groove 43. The anchor
line is then in both its ends more or less winded up on the anchor drum
wind up surface in two segments with helicoidal grooves 41 and 43, which
have helicoidal grooves in opposite directions. It is also possible to
divide the anchor line by a Y-coupling located a distance under the wave
energy converter, see FIG. 15a and the description below.

[0161]As will be described below, two anchor drums 9v, 9h can be placed on
either side of a centrally located counterweight drum 15. Helicoidal
grooves for resp. line 7, 17 can then be arranged in a way corresponding
to what is shown in FIG. 3c. The counterweight drum can then have two
segments with helicoidal grooves with opposite directions, this is not
shown.

[0162]As an alternative or a complement to the helicoidal grooves on the
winding up drums 9, 15 guide rollers 171 can be used to guide both
counterweight lines 17 and the anchor line 7 around resp. wind up drum,
see FIGS. 13a, 13b and 13c. The guide rollers are driven by threaded rods
173, which are rotated in pace with the drums. The threaded rods for
resp. counterweight drum 15 has screw-threads in the opposite direction
as seen in FIG. 13a, so that the counterweight lines 17 is guided in
opposite direction to each other, which is important for the centre of
gravity of the wave energy converter to remain centralized.

[0163]Two threaded rods 171 are used for each winding up drum 9, 15 and
these two are rotated by a common teeth belt or chain 175, which turns
belt- or chain-wheels 177. The guide ends of the guide rollers 171 are
connected to end pieces 179, through which the threaded rods passes and
which guides the guide rollers along the threaded rods. The guided
rollers are journalled in bearings at the end pieces and can rotate along
with resp. line 7, 17 to minimize friction and wear. The ends of the
threaded rods 173 are journalled in bearings at the driveshaft stay 141.

[0164]Yet another alternative to achieve safe wind up is to use trawl
drums, not shown, as is known from the fishing industry.

[0165]To minimize the risk that the counterweights 19, in the case where
two counterweights are used, and their lines 17 tangled with each other
the counterweights can be mechanically connected together by a suitable
stiff mechanical structure, which holds them physically separated from
each other. E.g. a counterweight frame 151 can be used, see FIGS. 3e and
3f. The counterweight frame can be shaped so that it does not rub against
the anchor line 7 and also prevent entanglement with it, e.g. with a
rectangular, quadratic or rhombic shape according to FIG. 3f or with the
shape of a closed curve, such as a round curve, not shown.

[0166]The buoy 3 can generally have the shape of a plate, which can be
oblong. Such an oblong plate can then in a convenient way be positioned,
so that it mostly has its longer end towards the wave direction. The
width of the buoy 3 can be adapted to the average wave length of the
waves at the sea surface, so that the buoy has a larger width at larger
medium wave length. Different methods can be used to stabilize the buoys'
position in relation to the wave direction. The rotating motion of the
water particles through the waves in combination with the traction force
towards the centre above the foundation 5 can be utilized by introducing
fins, see FIGS. 2d and 2e, on the buoy's 3 underside. Further the buoy's
shape can be adapted. The driveshaft 11 can instead of being centralized
under the buoy as shown in FIGS. 2a and 2b, in parallel with the plates
length going direction, be a bit displaced in the direction towards the
waves.

[0167]For the mounting of the transmission unit 2 inside the buoy 3, as
shown in FIGS. 2c, 2d and 2e, the buoy must have such a size, that it can
hold the transmission unit. Seen from the side, in parallel with the
driveshaft 11 the buoy can in this case have the shape in the form of an
ellipse, i.e. generally an elliptic cylinder. It can have a relatively
large section area against the water surface 6 at the same time as it can
be pulled against the wave direction with less water resistance compared
to a completely rectangular section area. The buoy 3 can have one or more
fins 4 in its back part, seen from the wave direction, which can
contribute to steering the buoy straight against the wave direction.

[0168]The transmission unit 2 in this design can be mounted in the
transmission unit space 20, whereby the transmission unit in whole or
partly can be made dry and thereby be protected against growth and
corrosion and a simpler and cheaper sealing solutions can also be used,
see FIGS. 2c, 2d, 2e and 2f. When the transmission unit space 20 is made
dry, it also contributes with its buoyancy to the buoyancy of the buoy 3.
The transmission unit space can for this purpose at the top be sealed by
a cover or a service hatch 121, so that the transmission unit space
constitutes an air pocket. To create and maintain the drainage of the
transmission unit space 20 an air pump 123 can be used. The air pump can
be driven by the link shaft 58, e.g. through a belt 125, and pump air
into the transmission unit space which gets the water level to be pushed
down, so that the transmission unit 2 is maid dry and the desired air
pocket is achieved. The air pump can be mounted at one of the shaft
frames 145, at which the driveshaft 11 is journalled in bearings. The air
pump 123 can alternatively be driven by an electrical motor, not shown.

[0169]When the wave energy converter is taken into operation, the service
hatch 121 over the transmission unit 2 is closed and the water level in
the transmission unit space 20 is pushed down by the air pressure, which
the air pump 123 produces. The water level outside varies during the wave
period correspondingly to the motive force between the sea floor
foundation 5 and the wave and also the mass-moment of inertia in
counterweight 19 and buoy 3. At service first of all the anchor drum 9 is
disconnected, then the pressure in the transmission unit space is leveled
to the air-pressure outside, so that the water level rises, and
thereafter the service hatch 121 can be opened and service be performed.
With the right dimensioning and when the motive force from the foundation
5 is disconnected the water level can be leveled just below the
driveshaft 11, so that sealings and air pump 123 never gets under the
water surface 6.

[0170]At major service the complete driveshaft frame 141 with including
components as shown in FIGS. 15g, 15h and 15i, can be lifted out and
replaced with a replacement unit. The counterweight 19 can be hitched
under the buoy 3 meanwhile the exchange is performed. Service of the wave
energy converter's transmission, generator and electronics can then be
performed ashore.

[0171]In the design with the transmission unit 2 and the driveshaft 11
placed centrally in the buoy 3 the buoy's angular modulation can be used
more efficiently. The buoy does follow the water surface, which gives an
angular modulation at troughs and wave crests. When the wave rises, the
driveshaft 11 rotates and the shaft stays 145 are then disengaged, so
that the buoy 3 can rotate backwards with the wave's waterline without
affecting the drive. When the waves turns downwards, the driveshaft is
locked against the shaft stays, which causes the driveshaft to turn
forward in pace with that the buoy following the angular modulation of
the wave. This in turn gets the counterweight drum 15 to rotate in
forward direction and act to accumulate energy in the counterweight 19 in
the same way as during the vertical motion in up going direction. The
larger diameter the anchor drum 9 has, the lower input rotation speed the
system gets in relation to vertical motion, while rotation speed from the
angular modulation is the same irrespective of the anchor drum's
diameter. The wave energy converter 1 can in this way be dimensioned with
a larger anchor drum 9 to achieve an enhanced effect from the angle
modulation in relation to the motive force from the vertical motion but
must then also have a large enough width to withstand the in the same
pace increased torque, which is transferred to the buoy 3 from the
counterweight 19, when the driveshaft 11 is locked against the shaft
stays 145.

[0172]The function of the wave energy converters 1 is with advantage
controlled by a computerized control system, not shown, which especially
controls the counterweight span level and compensates for varying
accelerations and retardations to achieve as equalized power level as
possible in relation to the current wave climate. The control system can
also be used for controlling the torque transfer in the anchor drum's
sliding clutch 55, 55' and the return feeding's sliding clutch 25, 25',
control of locking mechanisms, not shown, control hitching of
counterweight 19 and sea-floor foundation 5 in the driveshaft frame 141
at transport and service, and also logging of system function and wave
data. The control system is supplied with energy from a battery, not
shown, which is continuously charged by the generator 21.

[0173]The control system controls the counterweight span level and
monitors the wave energy converters 1 functionality with the help of
sensors, not shown, especially for rotation angles/speeds of the
rotatable parts, the generator's 21 electrical power output and the
buoy's 3 movements.

[0174]The control system can control the counterweight span level by
analysing data from a sensor, not shown, that is mounted in the
counterweight drum 15 and which continuously tells the system, at which
angle it has in relation to the gravitational direction or the shaft stay
13. The control system can thanks to this track the counterweight 19
position and turning points by calculating the number of revolutions of
the counterweight and exactly where it turns. The turning points for each
individual wave period are logged. An algorithm calculates if the
counterweight span has a tendency to drift upwards or downwards by
analysing the turning points during a time period. If the counterweight
span is drifting upwards, the counterweight 19 can be lowered in a
quicker pace, which leads to that a higher power output is generated from
the generator 21 and vice versa. The length on the time period is decided
from the accumulation capacity, i.e. the length of the counterweight line
17. The higher capacity, the longer time period can be used in the
calculation, which in turns gives smaller adjustments of the generator's
power output.

[0175]Two sensors, not shown, measure the electrical power output and the
rotation speed of the generator 21. These values are recalculated by the
control system to show the torque level over the generator. The control
system use the torque value to compensate for the counterweight's 19
g-force, which varies due to the mass-moment of inertia and affection by
the acceleration force and water resistance, which arises due to the
buoy's 3 motions in combination with variations of the driveshaft's 11
rotation speed. At a trough, the counterweight 19 is accelerated in a
direction away from the gravitational direction, which gives an increased
g-force, and at a crest the counterweight is acceleration a direction
back to the gravitational direction, which gives a lower g-force. By
regulating the counterweight's velocity of fall in accordance with the
varying torque, which loads the generator 21, the power level can be
stabilized.

[0176]As given from the discussion, for the counterweight's 19 turning
points not to drift to the end positions of the counterweight, the
counterweight's velocity of fall, i.e. the medium rotation speed of the
counterweight drum 15, must be balanced against the driveshaft's 11
rotation speed. When the medium turning point is moved downwards, the
counterweight's velocity of fall must be reduced, which leads to a
reduced power output from the generator 21 and vice versa. By regulating
the counterweight's velocity of fall and thereby the counterweight span
level the power output from the generator can be kept as even as possible
in relation to mean energy level in the current wave climate.

[0177]Regulation of the counterweight span level can be achieved in
different ways. Regulation of the electrical load on the generator is
likely the simplest and most cost efficient but there are also other
possibilities as described below.

[0178]The mechanical resistance in the generator 21 depends on the
electrical load, which is laid over the generator's poles. When the
electrical load is increased, the electromagnetic coupling over the air
gap 21'' in the generator is increased and thereby the mechanical
resistance in the generator, which gets the counterweight 19 to fall
slower, since the state of equilibrium between the generator and the
counterweight is moved to a lower rotation speed and vice versa, se the
regulation rule, which is shown in the diagram in FIG. 16a. Since the
generator's power is a product of the rotation speed and the torque, the
power level becomes even, meanwhile the rotation speed varies in the
opposite direction to the g-force and the input torque. This works due to
that the top rotation speed in a generator in general is higher than the
nominal rotation speed. The generator should manage a top rotation speed
that is at least 50% higher than the nominal.

[0179]At a constant electrical load a state of equilibrium becomes
present, i.e. the rotation speed of the generator 21 becomes present,
which gives an equally high mechanical resistance in the generator as the
motive force given by the counterweight 19, as earlier described. By
regulating the generator's ingoing mechanical torque the state of
equilibrium is displaced and thereby the rotation speed, at which the
state of equilibrium becomes present. The input torque can be adjusted
with a gear box with a so called variable gear ratio 37, CVT ("Continuous
Variable Transmission"), which can constitute or be included in the gear
23. A lower gear ratio gives a higher torque and a lower rotation speed,
which in turn balance each other out, but a higher torque also makes the
state of equilibrium, between the generator 21 and the counterweight 19,
to take place at a higher rotation speed, which increases the
counterweight's velocity of fall, and vice versa, compare with the
regulation rule, which is shown in diagram 16b. One type of CVT is CVET
("Continuous Variable Electronic Transmission") with input-output shafts
aligned, as schematically shown in FIGS. 12c, 12d. These figures are only
symbolic, since the manufacturer does not want to reveal details
regarding its mechanical design. Variable transmission gear boxes usually
only manage limited torques and a relatively low maximum gear ratio. To
minimize the ingoing torque and increase the gear ratio a planetary gear
35 can be coupled in before the variable transmission, as shown in FIG.
12c.

[0180]The return feeding's sliding clutch 25, 25' between the
counterweight drum 15 and the anchor drum 9, which according to above can
be used for keeping the anchor line 7 tensed, can at the same time be
used for reducing the torque given by the counterweight 19, which
displaces the generator's 21 and the counterweight's 19 state of
equilibrium in the same way as a variable gear does, see the regulation
rule shown in diagram in FIG. 16c and also compare with the diagram in
FIG. 16b. Full power of the generator and full speed of the counterweight
is reached, when the return feeding mechanism's sliding clutch 25, 25' is
completely disengaged, so that the full torque from the counterweight
loads the generator. When the medium wave height sinks, the torque in the
return feeding's sliding clutch increases, which lowers the torque over
the generator 21 and hereby the counterweight's velocity of fall is
reduced. As sliding clutch e.g. a magnetic particle clutch can be used,
which gives low heat losses at low rotation speeds. The torque can be
regulated very precisely with the help of the level of a feeding current,
so that the higher the current the higher the transferred torque becomes
and thereby also the higher break action.

[0181]By using a cone shaped counterweight drum, not shown, the radius for
the counterweight line 17 point of contact around the counterweight drum
can be increased the higher the counterweight 19 is winded up. The radius
and thereby the torque increases the higher the counterweight is hoisted
up and thereby makes the generator 21 to rotate faster. In this way, the
counterweight's 19 velocity of fall and the generator's power output
increases with an increased medium wave height. This principle for
regulation of the counterweight's span is self-regulating and hence does
not need to be regulated by a control system as the other methods, but
lacks the ability to compensate for variations in the counterweight's
g-force or the force with which the counterweight affects the drive
package, i.e. mainly the motive force in the counterweight line.

[0182]It is possible to design a wave energy converter 1 for automatic
installation. The starting position is then, that the sea-floor
foundation 5 and the counterweight 19 is hitched at the stay's 13 parts
or at the frame 141 with corresponding lines 7, 17 completely winded up.
The wave energy converter is connected to the electrical distribution
network and the control system is started. The disengagement mechanism
for the return blocking mechanism of the anchor drum is put in locked
position according to a control signal from the control system, so that
the anchor drum 7, cannot be disconnected, despite that the
counterweight/-s are in their top positions. In the shown designs this
means that the sliding clutch 55 mounted around the return blocking
mechanism of the anchor drum 51 is put on maximum force- or torque
transfer, which is enough to carry the entire weight of the sea-floor
foundation. The sliding clutch 25 of the return feeding mechanism can be
disengaged.

[0183]Then the control system loosens the hitches, not shown, that holds
the counterweight 19 and the sea-floor foundation 5, whereby the
sea-floor foundation starts to fall towards the bottom 8 of the
sea-floor. The anchor drum's line 7 is then unwound and the driveshaft 11
starts to rotate and drive the generator/generators 21. The control
system regulates for maximum power and thereby the sea-floor foundation's
5 velocity of fall is slowed down as much as possible, by the electrical
power that is produced. Further on the buoy 3 is preferably equipped with
an echo-sounder, not shown, that measures the water depth on the site,
where the installation takes place. The anchor drum 9 is equipped with
the same type of sensor, not shown, as is mounted on the counterweight
drum/-drums 15 and the control system can in this way measure how much of
the corresponding anchor line 7 that is unwound from the anchor drum. The
control system can with help of these values calculate when the sea-floor
foundation 5 starts to approach the bottom 8. To reduce the force of
impact the sea-floor foundation's velocity of fall is slowed down by
means of the return feeding sliding clutch 25. When the sea-floor
foundation 5 reaches the bottom 8, the driveshaft 11 stops to rotate and
the counterweight/-counterweights 19 instead starts to fall and continues
to drive the generator/-generators 21. The disengagement mechanism for
the anchor drum's 9 rotation in relation to the driveshaft is activated,
so that the anchor drum can rotate in one direction in relation to the
driveshaft. In the shown design this means, that the sliding clutch 55 in
the anchor drum is put in normal mode, which means that the by the
sliding clutch transferred force is reduced so that the force is not
enough to lift the sea-floor foundation 5. The control system is thereby
put into operation mode.

[0184]The outer electrical connection of the generator 21 can be achieved
without the use of slip rings, brushes and similar, even when the
generator stator'' 21 is mounted inside counterweight drum 15. The
generator stator 21'' includes, in a conventional way, electrical
windings, in which electrical power is induced at rotation and which are
connected to an electrical cable 41, which is partly winded up on the
counterweight drum in parallel with the counterweight line 17, see FIG.
4, but closer to the anchor drum 9. The electrical cable extends from the
counterweight drum 15 down to a movable connector 43, which can move
along the anchor line 7. At the connector the electrical cable 41 is
connected to yet another electrical cable 45, which e.g. extends to a
special connector buoy 45. Hereby the wave energy converter 1 can manage
to rotate, when the waves change direction, without lines and cables
getting entangled with each other.

[0185]Since the first electrical cable 41 is winded up on the same drum as
the counterweight 19, the connector 43 to will slide along the anchor
line 15 with mainly always the same distance below the counterweight.
Hereby it can be avoided that the counterweight and the electrical cables
41, 45 comes to close to each other.

[0186]At an alternative way for energy accumulation the energy can be
absorbed as a gas pressure in one or more tanks. Such a wave energy
converter 1 is schematically shown in FIG. 9a. Here the anchor drum 9
only needs to be connected to the driveshaft 11 via a return blocking
mechanism 53, compare the return blocking mechanism in the shaft stay 13
in FIGS. 5a and 5b. Any stays are not required, the driveshaft can
instead be journalled in bearings directly in the generator housing or
the generator casing 71, which replaces the counterweight drum 15 and
which in this case can enclose a fixed gear mechanism such as a planetary
gear 35, generator 21 and a compressor/gas pump 73. The casing is fixed
to the buoy 3, such as to its underside as shown in the figure or also
centralized in the buoy, if a transmission unit space 20 according to
above is used for mounting of the transmission unit 2. From the
compressor/gas pump 73 a gas pipe 75 runs to the gas tanks 77, preferably
located at or in the buoy. The gas tanks are also coupled to an over
pressure valve 79 and a pneumatic motor 81. At this motor's outgoing
shaft 85, gearwheel 87 is located, which acts together with teeth on the
anchor drum's 9 flange 31.

[0187]The compressor/gas pump 73 can be a so called scroll pump and it
then has a movable part 89, which is fixedly connected with the generator
21 stator 21'', and one to the housing 71 fixed part 91. The driveshaft's
return blocking mechanism 53 here acts against the housing.

[0188]When the driveshaft 11 is turned by the rising buoy 3 in this
design, a gas pressure is built up, by the scroll pump 73, in the gas
tanks 77. This gas pressure corresponds to accumulated energy. In pace
with the increasing gas pressure, the counteracting force against the
driveshaft rotation also increases. Higher waves, that give rise to a
quicker medium rotation speed of the driveshaft 11, thus build up a
higher gas pressure and which thereby gives a higher counteracting torque
between the generator rotor 21' and stator''. The control system hence
does not need to actively control and optimize the operation since the
equalization occurs through inertia in the pneumatic pressure. Since the
energy accumulation take place by a pneumatic pressure being built up,
the overpressure valve 79 can possibly be used instead of the sliding
clutch 53 between the anchor drum 9 and the driveshaft 11. The sliding
clutch though has an advantage by that it protects against thrust
strains. When the anchor drum 9 does not turn by its coupling to the
anchor line 7, as when the buoy 3 is sinking, it instead turns backwards
to stretch the anchor line by that the pneumatic motor 81 rotates and
drives the gearwheel 87, which acts on the flange 31 of the anchor drum.

[0189]Even with the use of gas return pressure it is possible to let the
generator stator 21'' be fixed to the buoy 3 and instead connect the
compressor 73 to the planetary gears 35 ring gear 165, see FIG. 9b. In
this case is the generator's stator is fixed to the generator housing 71.
The generator chassis 91 is also fixed to the generator housing,
meanwhile the compressor's 73 gear 95 on its driveshaft 93 is connected
to the planetary gear's ring gear, either directly as is shown or via a
teeth belt/chain. The ring gear rotates freely around the ingoing
driveshaft 11.

[0190]This design of the transmission unit 2 can have the following
advantages: [0191]No sling clutches are required in the anchor drum 9 or
in the return feeding mechanism. [0192]No counterweights are required and
thereby there is no g-force and no counterweight span that must be
regulated, since the higher wave, the higher gas pressure and torque over
the generator 21. [0193]Possible problems with counterweights and lines,
outer electrical cables, effect of accelerations, centre of gravity etc.
can come down completely or be reduced. [0194]The case that no
counterweight is used gives lower movable weight and thereby the
sea-floor foundation 5 can also be made smaller, i.e. with smaller mass.
The buoy's 3 lifting force can also be reduced with as much. [0195]Manage
shallower installation depth [0196]Only the anchor drum needs to be
exposed to the ocean water meanwhile other components can be
encapsulated. [0197]The housing for the gear mechanism and the generator
can be made with smaller diameter than the one in the earlier described
design used counterweight drum.

[0198]The same type of transmission unit 2 as have been described above
can be used in other designs of the wave energy converter as becomes
evident from FIGS. 7a, 7b and 7c. Instead of the sea-floor foundation
there are here sea-floor fastening devices 61, 63 fastened to the
sea-floor. 8. These sea-floor fastening devices are shaped like frames or
pillars, which reach upwards from the sea-floor, and the driveshaft 11 in
the transmission unit is journalled in bearings in the frames or at the
pillars. In FIGS. 7a and 7b two vertical pillars are used, which are
located completely beneath the water surface 6 and stretches up from the
sea-floor, and the driveshaft 11 in the transmission unit is journalled
in bearings to these pillars. In the designs according to FIGS. 7a and 7b
the anchor line 7 is fixed to the buoy. In FIG. 7b the transmission unit
is mounted so close to the bottom of the pool of water that the
counterweights are instead shaped like floating bodies 19'. The frame
according to FIG. 7c includes two vertical pillars, which reaches upwards
from the bottom 8 over the water surface 6 at the side of the buoy 3. The
pillars are at the top connected by a horizontal beam 64, which is
located above the buoy and from which stay parts similar to the stay 13
above protrudes downwards. The driveshaft 11 in the transmission unit is
journalled in bearings in these stay parts. It can be especially
observed, that at the design according to FIG. 7c, energy is absorbed
from the waves only when the water surface 6 and the buoy 3 sinks in
contrary to the other designs, where energy is only absorbed from the
waves, when the water surface and the buoy rises. Hereby the buoy must be
given a weight that is greater than the counterweight's 19 and be given
enough volume/buoyancy, so that it shall still be able to stay afloat at
the water surface 6. This is shown in FIG. 7c by that the buoy 3 is fixed
with a ballast 5''. In this design the counterweight 19 line 17 is winded
up around the counterweight drum 15, when the wave sinks, which
significantly reduces the motion span and variation in g-force. With the
right dimensioning and with periodical waves the counterweight can in
principle be held still. It is also possible to keep the counterweight
above the water surface 6, which gives a higher motive force in relation
to the counterweight's mass. This design is especially suited for places,
where there are already foundations, e.g. at wind power plants, where the
counterweight and its line 17 can run inside the mast, or at oil
platforms.

[0199]An alternative design of a wave energy converter 1 with a
transmission unit 215 according to FIG. 15a with a centrally, between two
anchor drums 9v, 9h located counterweight drum 15 is shown in FIG. 7d. In
this variant the driveshaft 11 is driven by a weight or load 211, which
hangs beneath the buoy 3 in an elastic organ 213, which for example can
include springs or air springs. At the weight the anchor lines are also
fixed. The weight 211 can have a considerable mass compared to the buoy 3
or generally in relation to other parts of the wave energy converter. The
forward drive of the driveshaft occurs through joint action between the
buoy 3 and the weight 211. When the buoy after having passed a wave crest
sinks, the buoy also moves downwards. Then when the buoy slows down and
turn in the next trough, the weight 211 continues due to its inertia to
first move downwards, which stretches and prolongs the elastic organ 213
and unwinds the anchor lines 17 so that the anchor drums 9v and 9h is
rotated and in turn drives the driveshaft to rotate. When the elastic
organs are prolonged, their traction force on the weight 211 increases,
so that its ongoing motion downwards is gradually stopped. Thereafter the
force from the elastic organs becomes so great, that the weight will move
upwards. This consequently occurs at the buoy's 3 rising movement. When
the buoy 3 then slows down again to turn in the next crest, the weight
continues to move upwards due to its mass-moment of inertia. The elastic
organs 213 are then pulled together and thereby their traction force on
the weight 211 is reduces, so that it is no longer balanced by the
gravity force, which affects the weight. At the same time the anchor
drums 9 can be returned and tense the anchor lines 7 for the next drive
of the driveshaft 11. The weight is then gradually slowed down to a stop
and after that again starts to move downwards.

[0200]The counterweight 7 runs through a through going hole in the weight
211 down to the counterweight 19, which moves with a phase shift to the
wave motion, which can reduce its vertical motion and reduce the size of
its accelerations and retardations at the wave motion, so that the
torque, which loads the generator 21, becomes a bit more even, which
thereby requires less regulation of the rotation speed. Such a design can
e.g. be advantageous at large water depths, where it can be difficult to
use an anchor line 7 fixed at the bottom 8 for driving of the driveshaft.

[0201]In one design, in which the wave energy converter is mounted in a
wind power plant, it is possible to integrate the transmission from the
turbine blades with the drive from the waves, so that the same gearbox
and generator can be used, see FIGS. 8a, 8b and 8c. The transmission can
closest be compared to the one shown in FIGS. 15a, 15b and 15e, which
shall be described below. The transmission model with a fixed stator
according to FIG. 15f can also be used in a similar way but this is not
described further here. The main difference is the mounting of the
planetary gear 25 in relation to the generator's stator. The function in
the planetary gear is in this design to combine the drive from the wind-
and wave motions, by letting the wind power plant's rotor rotate the
planet gear carrier 161, while the buoy 3 with ballast 5'' drives the
ring gear 165 of the planetary gear, see also FIGS. 12a and 12b. In this
way, the rotation and torque, which are obtained from the wind-resp. wave
motions, can be added to each other and together drive the sun gear 167.
Neither planet carrier nor ring gear is allowed to rotate backwards,
which for the planet carrier is achieved by the back locking mechanism 53
in the shaft stay 13 and for the ring gear by slipper clutch 201, which
has a function similar to a back locking mechanism. The slipper clutch
201 has the equivalent function as the anchor drum's slipper clutch, see
FIG. 5b and descriptions thereof, but is in this design located between
shaft stay 13 and planetary gear 35, which makes it possible to limit the
torque and energy absorption for both wind- and wave motions with one and
the same slipper clutch.

[0202]The generator 21 is mounted alone in the counterweight drum 15 with
connected counterweight 19, which gives the same equalization
capabilities as is described for the other designs. The return feeding of
the anchor drums is also done in the same way from the counterweight drum
15 via ring gear 29 and tooth band/chain 175 to the link shaft 58, which
in turn is coupled in the corresponding way to the anchor drums 9v and
9h. The diameter of the anchor drums 9v and 9h in combination with the
buoy 3 and the weight of the ballast 5'', determines the torque which is
put over the ring gear 165 of the planetary gear, and which rotation
speed the ring gear gets. These parameters are chosen to match the torque
from the wind turbine and the generator's size. As long as the torque,
which is obtained from the drive of wind and wave, is higher than the
counteracting torque, which is given by the counterweight 19, energy can
be accumulated in the counterweight 19 from both wind- and wave motions.
Since the torque from the wind power plant's rotor 204 varies dependently
on the wind-force while the torque from the wave drive is constant, it
may be necessary to mount a variable transmission gearbox before the
planetary gear in the same way as shown in FIG. 12e, but the variable
transmission gearbox in this design adjusts the torque from the wind
drive to the wave drive after the current wind-force. To prevent the
tower 207 of the wind power plant to be damaged by the buoy 3, some kind
of sledge mechanism is used, not shown, which guides the buoy along the
tower of the wind power plant. Breaking gearboxes is a big problem for
today's wind power plants. The transmission of the wave energy converter
can also be used in a wind power plant without wave drive to utilize its
capabilities to limit the torque and energy absorption. In this case the
same type of transmission design as described in FIG. 3d can be used but
without the anchor drum 9. The wind power plant's rotor is directly
connected to the driveshaft 11, as shown in FIGS. 8d and 8e. The
counterweight can run inside of the wind power plant's tower 207. When
used in a wind power plant, gas return pressure can also be used instead
of a counterweight as shown in FIG. 8f. This transmission design is
described in more detail in connection to FIG. 9b. The counterweight can
then be left out and its mass-moment of inertia will then not have any
effect, which can be of an advantage.

[0203]In the designs described above, the electromagnetic coupling between
the generator's 21 rotor and stator is utilized in most cases, while in
other cases an in a special way designed transmission is used for
achieving a continuous drive of the generator. Energy accumulation and
return feeding can be done in different ways. In general, a wave energy
converter 1 can include components as will be seen in FIG. 10a. An anchor
drum 9 included in a transmission unit 2 is in a suitable way
mechanically coupled to both a buoy 3 and to an object 8', which can be
considered to have a more fixed position than the buoy and which can be
constituted by the bottom, e.g. a bottom fastening device 5', also see
FIG. 10b, at which at least one of these two mechanical couplings 7'',
7''' includes an oblong organ, such as a flexible organ, typically a line
or a wire, but also a stiff shaft can be used in special cases. The
anchor drum can be located in a suitable way in relation to the buoy such
as under, inside or above. It can rotate in two directions as shown by
arrows 101, 102. The anchor drum 9 drives a driveshaft 11 at its rotation
in one direction, which can then only rotate in one direction, shown by
the arrow 103. The driveshaft is mechanically coupled to the generator
21, whereby the coupling is symbolically shown at 23'. The coupling
and/or the generator is set up in a way that a part of the rotational
energy is accumulated in an energy accumulation device 105 at the
rotation of the driveshaft 11. When the driveshaft is not able to turn
the generator, the energy accumulation device drives the generator
instead. The energy stored in the energy accumulation device can also be
used for returning the anchor drum 9 and for this purpose the energy
accumulation device can be coupled to the return feeding mechanism 107.

[0204]In the case which utilizes the electromagnetic coupling between the
generator's 21 two, in relation to each other rotatable parts, the
driveshaft 11 is mechanically coupled to the first part 21' by means of
the coupling 23', for driving this part to rotate in the direction shown
by the arrow 23, at which the electromagnetic coupling between the
generator's parts gives a torque corresponding to the driveshaft's
rotation and also gets the other part 21'' to rotate in the same
direction, se FIG. 10b. The generator's second part 21'' is in some way
coupled, so that it at the rotational motion, because of the driveshaft's
rotation, accumulates a part of the rotational energy in the energy
accumulation device 105. When the rotation speed of the driveshaft is
low, where it no longer is capable of turning the generators second part,
the energy accumulation device instead drives the generators second part
to rotate in the opposite direction as before.

[0205]In the designs described above, two generators 21 are used. However,
since the generator with belonging power electronics and gearbox, if any,
is a relatively costly part of the wave energy converter 1, designs with
only one generator can be more cost efficient. Below shall possible
designs with only one generator be described.

[0206]In a first design with two counterweights 19 and one to the buoy 3
fixed stator of the generator 21, see FIG. 14, there is also, as shown in
e.g. FIG. 26, a return feeding or link shaft 58. The link shaft couples
the movement of the two counterweight drums together, so that the motive
force from the right counterweight drum 15h is transferred to the left
counterweight drum 15v. The left counterweight drum includes a planetary
gear 35, which steps up the rotation speed of the generator, and also
limits the torque by means of the ring gear's coupling to the left
counterweight drum and the counterweight 19. The location of the wind up
drums are moreover the same as in the above described designs and
therefore, the buoy 3 in a wave energy converter designed in this way,
gets about the same stability or positioning towards the wave as in the
design with two generators. The generator 21 can be mounted in a separate
generator housing 181 with the generator's stator 21'' fixed to the buoy,
as shown in the figure, or alternatively in or at the left counterweight
drum 15v.

[0207]As shown, the link shaft 58 can be placed in front of the driveshaft
11 seen in the wave direction. This gives a better spacing when drifting
away from the sea floor foundation 5. The drifting brings the anchor
lines 7, which cannot be allowed to come into contact with the driveshaft
frame 141, to stretch out in a direction in relation to the counterweight
line in a slanting angle. Alternatively, the link shaft 58 can be placed
above the driveshaft 11, either in a slanting position or straight above.

[0208]Further on it is possible to design the transmission unit 2, so that
only one counterweight 19 is used without the wave energy converter
loosing stability or positioning towards the wave direction. Instead such
a design can, see FIG. 15a for a front view and 15b for a side view,
enhance the positioning in relation to the wave direction. The anchor
line 7 is divided in a Y-coupling 191 into two sub lines and these are
led to be winded up around one anchor drum 9v, 9h each, which are
positioned on each side of the single counter weight drum 15'. Guide
rollers 193, corresponding to the ones described for FIGS. 13a, 13b and
13c, diverts the sub lines, so that they are winded up correctly on the
anchor drums. The counterweight 19 runs free despite that the anchor
lines joins in a Y-coupling, since the point at the counterweight drum
and anchor drum where the resp. line is winded up is on the opposite side
of the driveshaft 11. The driftage from the foundation 5 also gives an
angle for the anchor line 7, 7', which gives extra margins. For further
safety margins the Y-coupling 191 can be placed below the lowest possible
position of the counterweight 19, not shown.

[0209]In FIGS. 15c and 15d an alternative of a straight wind up of the
divided anchor lines 7' around the anchor drum 9v and 9h is shown. A rod
221 holds the lines on a distance from each other and is placed just
above the Y-coupling 191. To decrease the risk of collision between sub
anchor lines 7' and the counterweight 19, the rod 221 can be placed below
the lowest possible position of the counterweight. One advantage with
this alternative is that the part of the anchor line 7, which connects
the rod 221 with the sea-floor foundation 5, can be more or less stiff
and e.g. be designed as a ground cable or chain, while the sub anchor
lines 7' can be more flexible for wind up around the anchor drums 9v and
9h. Further on the rod 221 can be designed to carry the load of itself
and the undivided anchor line 7, which then leads to that a lower force
is required for driving the return feeding, not shown in these figures.

[0210]In FIG. 15e the transmission unit in a wave energy converter is
shown according to FIGS. 15a and 15b seen from below and with more
details. The driveshaft 11 is here fixed only one of the anchor drums,
e.g. as shown with the left 15v. The left anchor drum 9v, the driveshaft
and the one and only anchor drum 15' has the same function and structure
as in earlier described designs, in which the generator 21 is build-in to
the counterweight drum. The second anchor drum, the right drum 9h, is
journalled in bearings so that it can rotate freely but its motive force
is transferred to the left anchor drum 9v by means of a link shaft 58.
The link shaft can be coupled via thereon mounted chain- or gear-wheels
203 to the anchor drums by means of chains or tooth bands 205, which also
runs over the toothed flanges 31. Alternatively the gearwheels 203 can be
directly connected to the anchor drums' flanges, in the same way as shown
in FIG. 2f. The return feeding of the anchor drums is done in the
corresponding way as earlier but the slipper clutch 25'' is in this case
coupled to the counterweight drum 15'.

[0211]In FIG. 15f an alternative to the transmission unit according to
FIG. 15e is shown. According to FIG. 15f the generator's stator 21'' is
fixed to the buoy 3 in a corresponding way as shown in FIG. 2g. The
generator casing 71 is placed on one side of the single, centrally placed
counterweight drum 15', which results in that the transmission unit 2
must be made wider. The anchor drums 9v, 9h must be placed with an equal
distance from the counterweight drum for the traction force by the
counterweight 19 and the foundation 5 via the counterweight lines 7'
shall remain centred in the wave energy converter. This leads to that
more stay parts or shaft stays 13, 145 are required to carry the parts of
the transmission units. It is possible to use the same design of the
anchor drums as described above for FIG. 15e. However, in this case it
can be motivated to simplify the left anchor drum 9v by using an
displaced or free lying slipper clutch 55' and use the extra space in the
transmission casing space 20 for the transmission unit 2, so that the
left anchor drum 9v can be fixed to the driveshaft's first part 11' in
the same way as earlier described for FIG. 5c while the driveshaft's
second part 11'' on the other side of the slipper clutch comprises or is
directly connected to the ingoing shaft to the gear 23 and the
counterweight 15' rotates around this second part.

[0212]In FIGS. 15g and 15h an alternative transmission unit according to
FIG. 15f is shown, in which the mechanics is to a larger extent
encapsulated. The power transmission between driveshaft 11', 11'' and the
link shaft 58 can in this design preferably be done via gearwheels 209. A
high gear ratio as shown in the figure is used for increasing the
rotation speed of the link shaft and decreasing the torque which gives
less wear and smaller dimensions of the power transmission. In this
design only the drums 9v, 9h, 15' are exposed to the sea water in the
transmission housing 20. The generator 21 with all belonging power
electronics and the link shaft 58 including the power transmission are
encapsulated in a climate controlled environment 195. The return feeding
26 has in this design been placed on the high speed side of the gear 35,
but could also be placed on the low speed side. One advantage with
placing the return feeding 26 on the high speed side is that the space
will be used more efficiently since it requires a higher gear ratio in
the return feeding compared to the link shafts power transmission 210. A
high speed rotation in the slipper clutch gives higher transmission
losses though.

[0213]In FIG. 15i an alternative to return feeding, which is described in
relation to FIG. 15g is shown. Here an electric motor 223 is used
instead, which is directly connected to any of the gearwheels 209 on the
link shaft 58. The electric motor gets power from the battery, not shown,
which drives the control system and other electronics, not shown. The
electric motor is controlled by the control system which in that way can
optimize the return feeding. It is also possible to drive the return
feeding by means of a spring mechanism, such as e.g. a coiled spring or a
constant power spring, not shown.

[0214]A wave energy converter has here been described which can have one
or more of the following advantages: [0215]The counterweight drum/drums
limit the maximum resistance in the system and give a sharp limit for the
torque acting over the generators. [0216]The energy accumulation is very
simple and efficient and can store energy over long time intervals at the
same time as the motive force can be held constant in relation to the
average wave height during the time interval. [0217]The wave energy
converter can be dimensioned to utilize the depth on the installation
site in an optimal way for the accumulation and for decreasing the weight
of the counterweight. [0218]The storage of energy is stopped
automatically when "the accumulator is full" and this can be achieved
without the generator losing power. [0219]The scalability is very good
and the wave energy converter can be dimensioned to reach maximum
capacity at a selected wave height to get a better utilization factor of
the generator. [0220]It is not necessary to over dimension the whole
system to be able to handle absorption of energy at rare occasions when
the mean wave height is considerably higher than normal. [0221]The buoy
continuously follows the wave motions independently of how large the
waves are. The force limitation in the anchor drum efficiently protects
the device from thrusts and overloads. [0222]The motive force is constant
in relation to the gear ratio which enables the use of all types of
generators, incl. synchronous AC generators, which are working with
constant or variable rotation speed. [0223]Minimal manual efforts at
installation, short course of installation which generators electricity
already when the foundation is being lowered down. [0224]Mainly simple
and durable construction. [0225]Very high utilization factor of the
generator and transmission. [0226]Long service intervals.

[0227]While specific embodiments of the invention have been illustrated
and described herein, it is realized that numerous other embodiments may
be envisaged and that numerous additional advantages, modifications and
changes will readily occur to those skilled in the art without departing
from the spirit and scope of the invention. Therefore, the invention in
its broader aspects is not limited to the specific details,
representative devices and illustrated examples shown and described
herein. Accordingly, various modifications may be made without departing
from the spirit or scope of the general inventive concept as defined by
the appended claims and their equivalents. It is therefore to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within a true spirit and scope of the
invention. Numerous other embodiments may be envisaged without departing
from the spirit and scope of the invention.